The influence of curvature radius of the cavity mirrors on the performance of high power single frequency laser is investigated. When the cavity length is kept constant, both the pump power at the optimal operation point and the maximum output power decrease with the increase of curvature radius of the cavity mirrors beside the gain medium. However, if the cavity length is shorten to a certain extent, the pump power at the optimal operation point and the maximun output power can be recovered. The experimental results are consistent with the theoretical expectation.