Abstract: The content of water vapor in atmosphere is very little, but it is the most active molecule in atmosphere. The volume ratio of moisture to air was about 0.1%-4% and most part water vapor concentration in the troposphere. The influences of atmospheric attenuation become more serious along with the development of the optics-electron detecting technology. The water vapor in the atmosphere was the main factor and uncertain parameter to affect atmospheric attenuation. Infradred wavelengths was commonly used in photoelectric detection, but water vapor makes great effect on the radiation absorption due to its high concentration. Raman lidar has become the useful advantaged tools to measure water vapor. The system structure and specifications of Raman lidar developed by introduced. The measurement results show that this lidar can take measurements of water vapor over 8 km height at night and water vapor in boundary layer in day time as well as the tropospheric aerosol in day and night continuously. The obtained results are better consistent with radiosonde data in terms of the water vapor, which assures the reliability and availability of the Raman lidar for water vapor observation.