Abstract: Joint observation using Lidar and millimeter wave cloud radar(MWCR) from which more comprehensive properties of cirrus can be retrieved is the main trend of cirrus observation. Combining the information of cirrus boundary from Lidar and MWCR of ARM project, more accurate boundary of cirrus was obtained. Joint inversion method for retrieving cirrus microphysical properties was presented. Both ice water content and optical depth can be inverted accurately even in cases when the cirrus can't be penetrated by Lidar or can't be sensed by the MWCR through this method. The joint method was applied to a cirrus case, the results showed the accuracy of ice path content increased by 24% when the Lidar can't penetrate the cirrus and 48% when the MWCR can't sense the cirrus. Based on the accurate inversion of ice water content, the optical depth of cirrus was obtained using the relationship between ice water content, size distribution and optical depth. The inversion method of optical depth can overcome the difficulty arise from the attenuation of cirrus to Lidar.