By statistical analysis of Doppler radar velocity field data of fortythre e rai nfall processes from June 2003 to October 2005 at Dalian district, the effects o f radar velocity field characters on future rainfall variation and precipitation enhancement condition were gained, the indications of several familiar echo vel ocity characters of the cloud systems on the developing changes of the coming ra infall were obtained. Several criterions were concluded for analyzing the precip itation potential region and the opportunity for precipitation enhancement opera tion while radar echo showed “s” or bow shape. By using these characters as as sistant criterions in precipitation enhancement command, the practical validatio n showed good results in the precipitation enhancement operation at Dalian distr ict in spring and summer of 2006. These criterions have become as important estimating indexes in the realtime precipitation enhancement operat ion control at Dalian district.