Mechanism for compressive strength increase of recycled coarse aggregate concrete(RCAC) was analyzed, and compressive strength tests of RCAC were conducted at 1, 2, 3, 5, 7, 14 and 28d ages. A concept, named half value strength index, for age strength model of RCAC was proposed and employed. Combined with initial hardening rate and final strength, mathematical age strength model is established in order to reveal deficiency of conventional hyperbolic age strength model. Mathematical characteristic that ideal age strength model should have is pointed out. A new age strength model of RCAC is presented which can overcome the deficiency of conventional age strength model. Finally, good agreements have been found between tested data and new model simulations.