In this paper ,through optimum design to passively Q-switched by Cr∶YAGat 946nm ,we choice the gain crystal ,Q-switched crystal ,length of the cavity and optimum focusing.With 1. 2W incident pump power ,we get 946nm continuous infrared output power as high as 160mW,average power 70mW at passively Q-switched ,the peak-power up to 200W.By extra cavity frequency doubling ,an output power of 1. 5mW at 473nm was generated. The efficiency of optic2optic is 2. 2 % ,and this is highest power in the same condition in China.