In high average power lasers, local heating of frequency doubling crystals induced by the residual absorption at the interacting frequencies leads to the destruction of the perfect phase matching condition, which drastically reduces the conversion efficiencies to the second-harmonic generation. In order to obtain high efficiency SHG output, a temperature control system is developed using a semiconductor cooler to acljust the temperature and a temperature sensor AD590 as the temperature measurement component The temperature accuracy is 0.1 ℃.