Abstract:To study the performance of millimeter wavelength cloud radar in detecting cloud over Xinbu city of Beijing,this paper uses the data detected by millimeter wavelength cloud radar of Beijing observatory in November 2016 and Yanqing observatory in January 2018 as well as CL51 laser-ceilometer to compare cloud detection capability of two radars.The ability of obtaining high,medium and low clouds between two instruments are made a comparison.And the cloud base height detected by the two instruments is also compared.The results provide the references for other stations to further study on cloud differences of the two cloud measurement instruments.