A dual Fabry-Perot etalon with high spectral resolution is used as the frequency discriminator in the wind detection system. Simulations of the system at 1064nm using reasonable instrumental parameters are used to show the effects of the imperfections and the beam divergence to the etalon. The frequency center distance between the dual channels wasmeasured from interferograms. Transmissions of the dual channels are also measured with CW laser and Q-switched pulse laser. Comparisons have been made between experiment data and theoretically derived transmission functionswith designed parameters. System error ranges from 0. 42 m / s to 0. 85 m / s for a long period of 22 days.