The law signed Wednesday trims benefits for any state workers hired after Jan. 1. It also caps the maximum pension benefit and raises the retirement age.
Quinn called the action "historic" and said it could convince people to back an income tax increase for education.
Any income over $106,800 would not be included in calculating a pension. The retirement age jumps to 67 and annual adjustments would be tied to inflation and not compounded.
Labor unions opposed the measure and point out it does nothing to pay Illinois' current outstanding pension liability of $80 billion. The Pew Center on the States in February called Illinois the worst in the nation in funding its pension program.