Aiming at WDM transmission of wideband RF signal in electronic warfare system, this paper gave the influence rule of key parameters in microwave photonic link on spurious signal through theoretical analysis, and put forward the optimization method of non-uniform channel spacing assignment. By fine-tuning the wavelength of each channel, the frequency of spurious signals generated by four-wave mixing exceeded the bandwidth of the EW receiver, so as to reduce the influence of spurious signals on the system. The scheme was simple to implement and had good engineering implementability without changing the existing electronic warfare system architecture. The experimental results show that, compared with the uniform wavelength intervals, when the 5-channel non-uniform WDM signals is transmitted for 1km, the spurious signals caused by four-wave mixing in the receiver bandwidth are significantly optimized, and the dynamic range is increased by more than 26dB.