Starting in 2012 it will trim guaranteed admission from the top 12.5 percent of the state's high school graduates to the top ten percent.
Opponents say it will have a devastating effect on diversity in the UC system.
One study says African American enrollment, for example, would drop 27 percent.
"It's in the interest of all of us as a legislator, as elected officials, as parents, as university regents to have a diverse California that really reflects the population," Assemblyman Mike Eng, D-Monterey Park said.
California's constitution allows the UC system to control its admission policies without state oversight.