Abstract: To improve the accuracy of winter rainstorm forecasting, timely provide weather service for the government and people, and reduce the loss of agricultural production, the authors did real-time analysis, synoptic analysis, diagnosis analysis of moist potential vorticity (MPV) of 2 winter rainstorms resulting in agricultural disasters occurred on January 27 to 28, 2016 and December 13 to 16, 2013 in Guangxi, by using the precipitation data from automatic weather stations and NECP FNL analysis data. The results showed that: the rainstorm occurred in negative or near the zero line before the positive side of MPV1 and the low zone of the south of MPV2 negative center; MPV1 and MPV2 had some indicating significance for the 2 types of precipitation areas, MPV1 center could not decide the frontal rainstorm precipitation fall area, but had the forecast potentiality for precipitation, MPV2 could forecast the occurrence of heavy rain in advance. MPV isoline-intensive area, the meet of cold and warm air strongly is beneficial to moisture convergence, and the development of vertical vorticity is easy to produce rainstorm.