Abstract: The calibration of water vapor mixing ratio is an important issue for Raman lidar. A dual wavelength lidar was developed and tested for the self-calibration of water vapor mixing ratio based on the two YAG laser, which emitted laser pulses at the wavelengths of 532.1 nm and 659.7 nm. From the analysis of the lidar measurements, it indicates that the capability of lidar satisfies with the requirements of water vapor mixing ratio self-calibration completely. In the altitude range, in which the measured aerosol liar scattering ratio was about 1.01, the calibration constant of nitrogen mixing ratio was determined to be 0.5450.031 from the lidar measurements, and the relative uncertainty was about 5.7%. The determination of the nitrogen mixing ratio calibration constant was the key step in the water vapor mixing ratio self-calibration, which lays a foundation for the self-calibration could and the water vapor mixing ratio.