The officer was hit by a sedan near Nichols Road at about 4:30 p.m. and he was airlifted to a hospital, prompting a closure of the southbound lanes.
The officer killed was later identified by CHP in a social media post as Sgt. Steve Licon.
"Our hearts are heavy after the immeasurable loss of a friend, father, husband, and hero," the social media post said.
Licon was on the shoulder of the freeway issuing a citation to another driver when the 37-year-old driver of the sedan hit him, authorities said.
"He was in the process of issuing a citation to a motorist, shortly after that, an errant driver that was under the influence of alcohol drove onto the shoulder of the freeway, striking the sergeant's motorcycle and the vehicle that was initially pulled over," a CHP official said.
Witnesses rushed to help the officer before he was airlifted to the hospital, where he was pronounced dead.
Traffic was snarled for miles as the southbound lanes of the freeway were fully closed from Indian Truck Trail to Nichols Road due to a police investigation, Caltrans said. Lanes on the southbound side are expected to remain closed for several more hours.
Injuries sustained by the driver in the sedan were not immediately known.
A procession stretching more than a mile long made its way to the Riverside County coroner's office in Perris from a hospital in Wildomar as Licon's body was transported. .
Licon, a 27-year veteran, was set to retire next year. He is survived by his wife Ann, daughter Marissa and step-daughter Kelly.
Acting Governor Kounalakis has ordered Capitol flags to be flown at half-staff in his honor.