Aiming at the current explosive growth of information and the higher demand for communication channel capacity，taking image transmission as an example，the transmission results of images transmitted through additive Gaussian noise channel and Rician channel under two common modulation methods in laser communication，OOK modulation and QPSK modulation，are simulated and compared in MATLAB software. At the same time，the error rate curves under two modulation methods are also compared. The simulation results show that regardless of the modulation method，the received image will significantly deteriorate with the increase of noise，but the degradation speed of additive Gaussian channel is slower than that of Rice channel. Under the same channel conditions，the degradation of images after QPSK modulation is better than that of OOK modulation. The comparison of error rates shows that the QPSK modulation method has a significantly better error rate than OOK modulation. Through the simulation results，it is concluded that QPSK modulation has its unique advantages over OOK modulation in noise environment，which provides a reference for the selection of modulation methods in laser communication systems.