The microstructure, mechanical properties and annealing behaviors of Cu-Zn-Si alloy subjected to cryorolling was investigated by transmission electron microscope, tensile tests and microhardness measurement. It was found that cryorolling encouraged twinning and dislocation accumulation in Cu-Zn-Si alloy, leading to the distinct enhancement of tensile strength and microhardness. Furthermore, cryorolling could provide more nucleation sites for static recrystallization than cold rolling does. After annealing, cryorolled samples owned more excellent combination of strength and ductility than cold rolled ones, owing to the nanotwins generated by cryorolling and finer grains. A tensile strength of 787 MPa and an elongation to failure of 14.3% were obtained for Cu-Zn-Si alloy after cryorolling followed by annealing at 280 ℃ for 5 hours.