It is necessary to estimate accurately the influencing weather systems at the beginning of operation and develop conceptive synoptic models for precipitation enhancement operation in Liaoning Province in order to make artificial precipitation operation more effective. Four types of synoptic models (westerly trough, northeast cold cyclone, shear linear, and subtropical high) are establish ed, based on the analysis of the characteristics of atmospheric circulation affecting precipitation over Liaoning Province and the survey of the upperlevel and ground weather charts of the Eurasian region from 1983 to 1992. The precautionary areas for the next 12 to 24 hours and the optimized seeding areas can be given for precipitation enhancement in Liaoning Province.