The Imperial Senate was kept as a facade to hide the absolutist ruling of the Emperor. It still claimed to have legislative functions, but it actually had no authority.

From wookiepedia:

Whereas the Galactic Senate had held both legislative and executive power, the Imperial Senate held only legislative power—though most of this power was in the hands of the Emperor, as he was the overall ultimate authority. Despite such, the Imperial Senate still held limited judicial authority, enough to try high ranking officials in the Empire and, possibly, handle cases tied into the Supreme Court. The Emperor allowed the Senate to provide him counsel in enacting new laws. It also had nominal oversight of the Imperial bureaucracy and worked on the Imperial budget. However, the Emperor made it clear that his judgments would be final: Imperial decrees would be issued without debates, court proceedings, or Senatorial overrides. The Emperor could also call and dismiss the Senate at will.

So, it was only a puppet, although not easy to control; later on some of the senators began working against the Empire, hence why it was eventually dissolved by Palpatine.

Although at the time of the Empire's formation a majority of senators were loyal to Palpatine, the Imperial Senate was still a prime (if often clandestine) source of resistance to Palpatine's authority, and despite its changes, came to be known as the "last remnants of the Old Republic." Certain Senators—many of whom later joined the Rebellion—were known for using the Senate as a platform to voice proposals attempting to moderate Palpatine's rule, although always under the guise of perfect loyalty, and some also proceeded to secretly give aid to the Rebel Alliance.

The Imperial Senate was kept as a facade to hide the absolutist ruling of the Emperor. It still claimed to have legislative functions, but it actually had no authority.

From Wookieepedia:

Whereas the Galactic Senate had held both legislative and executive power, the Imperial Senate held only legislative power—though most of this power was in the hands of the Emperor, as he was the overall ultimate authority. Despite such, the Imperial Senate still held limited judicial authority, enough to try high ranking officials in the Empire and, possibly, handle cases tied into the Supreme Court. The Emperor allowed the Senate to provide him counsel in enacting new laws. It also had nominal oversight of the Imperial bureaucracy and worked on the Imperial budget. However, the Emperor made it clear that his judgments would be final: Imperial decrees would be issued without debates, court proceedings, or Senatorial overrides. The Emperor could also call and dismiss the Senate at will.

So, it was only a puppet, although not easy to control; later on some of the senators began working against the Empire, hence why it was eventually dissolved by Palpatine.

Although at the time of the Empire's formation a majority of senators were loyal to Palpatine, the Imperial Senate was still a prime (if often clandestine) source of resistance to Palpatine's authority, and despite its changes, came to be known as the "last remnants of the Old Republic." Certain Senators—many of whom later joined the Rebellion—were known for using the Senate as a platform to voice proposals attempting to moderate Palpatine's rule, although always under the guise of perfect loyalty, and some also proceeded to secretly give aid to the Rebel Alliance.

Whereas the Galactic Senate had held both legislative and executive power, the Imperial Senate held only legislative power—though most of this power was in the hands of the Emperor, as he was the overall ultimate authority. Despite such, the Imperial Senate still held limited judicial authority, enough to try high ranking officials in the Empire and, possibly, handle cases tied into the Supreme Court. The Emperor allowed the Senate to provide him counsel in enacting new laws. It also had nominal oversight of the Imperial bureaucracy and worked on the Imperial budget. However, the Emperor made it clear that his judgments would be final: Imperial decrees would be issued without debates, court proceedings, or Senatorial overrides. The Emperor could also call and dismiss the Senate at will.

Although at the time of the Empire's formation a majority of senators were loyal to Palpatine, the Imperial Senate was still a prime (if often clandestine) source of resistance to Palpatine's authority, and despite its changes, came to be known as the "last remnants of the Old Republic." Certain Senators—many of whom later joined the Rebellion—were known for using the Senate as a platform to voice proposals attempting to moderate Palpatine's rule, although always under the guise of perfect loyalty, and some also proceeded to secretly give aid to the Rebel Alliance.

Whereas the Galactic Senate had held both legislative and executive power, the Imperial Senate held only legislative power—though most of this power was in the hands of the Emperor, as he was the overall ultimate authority. Despite such, the Imperial Senate still held limited judicial authority, enough to try high ranking officials in the Empire and, possibly, handle cases tied into the Supreme Court. The Emperor allowed the Senate to provide him counsel in enacting new laws. It also had nominal oversight of the Imperial bureaucracy and worked on the Imperial budget. However, the Emperor made it clear that his judgments would be final: Imperial decrees would be issued without debates, court proceedings, or Senatorial overrides. The Emperor could also call and dismiss the Senate at will.

Although at the time of the Empire's formation a majority of senators were loyal to Palpatine, the Imperial Senate was still a prime (if often clandestine) source of resistance to Palpatine's authority, and despite its changes, came to be known as the "last remnants of the Old Republic." Certain Senators—many of whom later joined the Rebellion—were known for using the Senate as a platform to voice proposals attempting to moderate Palpatine's rule, although always under the guise of perfect loyalty, and some also proceeded to secretly give aid to the Rebel Alliance.