To improve the data quality of Ka band millimeter wave cloud radar, a quality control method for solving problems related to velocity aliasing, noisy echo, data missing and plankton contamination is presented. The effectiveness of the method was verified by several cases. The results show that the velocity dealiasing algorithm based on radar Doppler spectra processing is effective with high success rate and stability. Success rates of 15 cases reach 100%. It can also find out the fuzzy type and correct radial velocity and spectrum width. With this method, noisy clutter are filtered validly and missing data can be filling well. The plankton echoes can almost be removed clearly while the small scale cloud can be remained.