A dual-frequency ratio frequency discrimination technique for Rayleigh wind measurement lidar was proposed. The basic principles of molecular scattering Doppler wind lidar were introduced, and the optical path structure of the frequency discrimination system was analyzed. Based on the detection requirements, the parameters of the Fabry-Perot etalon in the frequency discrimination system, including the free spectral range (FSR), full width at half maximum (FWHM), and dual-frequency laser interval, were optimized in detail. Using the overall system design parameters, theoretical simulations were conducted on the system's velocity sensitivity, signal-to-noise ratio (SNR), and measurement accuracy.