Lidar or laser radar is widely used in the spatial and temporal distri bution detection of atmospheric aerosols and clouds because of its unique advantages in technology. From June 20to July 20,9,the mobile Doppler wind lidar developed by Ocean University of China was o perated in Zhuhai National Climate Observatory(N22° 4’,E113°12’)for a tmospheric observation,especially for winds, aerosols and clouds profiling.This paper focuses on the lidar observation of at mospheric cloud and cloud base height retrieval.With the detection range of 0.3-20km,56groups of effec tive atmospheric backscattering profile data were obtained and recorded.Cloud-base height is st udied and retrieved with the improved differential zero-crossing method based on the measuring backscatterin g data.According to the measurement time and signal to noise ratio,three different thresholds are inves tigated and added to the zero-crossing process of the backscattering profile.Compared with the clear ai r,retrieved adjacent layers merging into one layer or discriminated into different layers are also considere d.The result statistics of this observation period show that the minimum and maximum of the observed cloud base height are 0.55km and 13.51km,respectively.It is found that the algorithm can realize precise detection of cloud base automatically with a 10m report height accuracy.