Abstract: The Fabry-Perot etalon was the key component of a Rayleigh Doppler wind lidar. In order to accurately determine the Doppler shift proportional to the wind velocity, the principle of Rayleigh Doppler frequency measurement was deeply analyzed, and the optimum parameters of the etalon were determined after analyzing the detection error at the maximum height designed. The calibration method and idea were introduced in detail. The factors making the full width at half maximum(FWHM) of the transmission curves broadened were analyzed, the calibration accuracy of the transmission curve affecting the velocity sensitivity and the system measuring error was also analyzed in detail. The design and calibration were verified in experiments. The result indicated that the velocity sensitivity of etalon decreased 0.118%/(m·s-1) due to the broadened FWHM of transmission curves and with the signal-to-noise ratio no less than 10, the accuracy of the line-of-sight velocity increased 2m/s at 40km altitude height.