Shane Hampson, 23, of Lime Grove, Skelmersdale, was convicted at Liverpool Crown Court last month of causing death by dangerous driving.
John Gregory, 49, from Wigan, Greater Manchester, died when the car crashed into the back of his vehicle in Skelmersdale, in February last year.
Hampson was also handed a four-year driving ban.
Police said Mr Gregory was driving his Chrysler Voyager home from work along Grimshaw Road when Hampson crashed into it from behind.
Mr Gregory's car overturned and he died at the scene.
Another car was also struck but the driver escaped unhurt.
Sgt Patrick Worden, from the Road Policing Unit, said: "I am very pleased with the sentence Hampson has been given and I hope this will serve as a warning to those who choose to behave in this manner - you will be punished.
"John Gregory was simply driving home from work when his car was struck from behind by a Volvo driven by Shane Hampson.
"As a result of the collision, the Chrysler overturned during which Mr Gregory was ejected from the car causing him significant injuries."
He added: "It was evident Hampson has been travelling at extremely high speed at the time of the collision and a lengthy investigation followed which identified that Hampson had driven dangerously not only at the time of the collision but within a few miles of the collision site.
"Despite claiming his innocence throughout, Hampson was convicted by a unanimous jury and I hope that this case sends out a strong message about the consequences of speeding."
A driver who caused a man's death when he crashed into the back of a car has been jailed for four years.