Reflectivity calibration error, attenuation in rain area and water cover over cloud radar antenna had serious effects on retrieved microphysical and dynamic parameters with reflectivity spectral density data, it is key problem to analyze these errors in retrieving microphysical and dynamic parameters. Aiming at reduce the effects of observation bias of reflectivity introduced by calibration and attenuation of water cover over cloud radar antenna, a retrieval algorithm for air vertical motion (Vair) and raindrop size distribution (DSD) based on reflectivity spectral density data and dual wavelength ratio (DWR) constraint with Ka/Ku dual-wavelength cloud radar (DWCR) are presented in this paper, The disdrometer data were used to examine the retrieved parameters. The effects of air vertical speed on retrieved microphysical parameters are discussed. In the algorithm (DWR-SZ), Vair retrieved from single Ka/Ku band CR (ST) and DWCR algorithms (DWSZ) are merged to form Vair in all of observation area, then the initial DSD and attenuation are retrieved by using DWSZ algorithm. Finally, DWR between first and last ranges in liquid area in a beam are used to adjust the reflectivity bias and retrieved final DSD to minimize the difference between the cloud radar observed and calculated DWR. Two convective precipitation cases in June 8, 2020 and June 1 2021 in Longmen, Guangdong Province, are used to examine the retrieved results. The results show that the radar sensitivity variations have little effects on Vair retrieved from DWSZ, however, the DWSZ cloud only used in the areas containing big rain drop (diameter large larger than 1.8mm). ST algorithms wit Ka and Ku data underestimated Vair, however, the Vair are reasonable in low levels with reflectivity weaker than 35dBZ. Highly sensitive work mode with pulse compressions could improve the Vair retrieval bias. Merged Vair from ST and DWSZ algorithms are reasonable. The attenuation and far radar range could introduce the underestimations of Vair with ST algorithms, the underestimations of Vair in solid precipitation area are negational due the sharp variation and narrow of reflectivity spectral density data. Using constraint condition of DWR reduced the bias of observed reflectivity and effects of water cover over antenna, improve the retrieval results. Vair from ST used in DWR-SZ overestimated drop number, liquid water content (LWC) and attenuation coefficient and underestimated drop size, however, it has no effects on reflectivity bias produced by water cover over antenna.