Mach-Zehnder (M-Z) interferometer can be used in Doppler lidar for wind measurement as frequency discriminator. The common M-Z interferometer′s stability is poor and not easy to adjust. A new type dual-channel M-Z interferometer was proposed as frequency discriminator based on dual prism. Through analyzing the wind measurement theory, the system was optimized and designed with optical design software. The wind velocity was retrieved from simulation result through setting experiment parameter. Compared with the theoretical wind velocity calculated from Doppler frequency shift formula, the result indicates that the retrieval simulation wind velocity agrees with theoretical wind velocity; the standard deviation is 0.46 m/s. So the new type structure can be applied in Doppler wind lidar as frequency discriminator. The optical path is easy to adjust and the system stability is improved.