Aiming at the problem that the channel gain of the multi-channel radio frequency optical transmission module based on the wavelength division multiplexing technology is small, the channel gain fluctuates greatly due to the spurious signals in the bandwidth generated by the four-wave mixing effect and the wavelength drift at high and low temperature. Based on the principle of frequency mixing and wavelength tuning of the optical transmitter, a solution to the gain fluctuation and in-band spurious of the multi-channel radio frequency optical transmission module is designed. The optimization algorithm of wavelength combina-tion is used to calculate a set of wavelength values that meet the requirements, and the optical transmitter is tuned by temperature. wavelength, and experimentally verified using a tuning system based on tuned wavelengths. The experimental results show that the scheme can debug the spurious signal outside the working bandwidth, and the full temperature gain change of the same channel and the same frequency point is less than 2 dB.