The inland plateau lakes account for 57.2% of the total lake area in China，which is an important research object for environmental and climate resources. As a large number of plateau lakes are located in uninhabited areas and cover a large area，the actual observation data of plateau lakes are very limited at present. In order to solve the monitoring problem of plateau lakes in uninhabited areas，a high-precision photon counting lidar on unmanned aerial vehicle platform was studied，a detection probability model of single photon detector was established，and the theoretical relationship between the signal level of lidar，the number of receiving channels and drift error was derived. In order to further reduce the drift error of photon counting lidar，a photon counting lidar receiving optical system based on four-channel detection with a working wavelength of 532±0.1 nm，a system aperture of 50 mm，an angle of field of 0.2 mrad，and a propagation distance of 2~3 km was designed. Through optimization design，the system aberration index met the design requirements，and the energy efficiency of the spectroscope group was 83.87%. The structure was reasonable，which can provide a reference for the application of multi-channel photon counting lidar optical system in lake monitoring.