In this paper, the synoptic background, the nongeostropic 〖WTHX〗Q〖WTBZ〗vector contribution and the phase change of the conditions are analyzed in the process of heavy snowstorm and heavy rain in Northeast China during March 3-6, 2007. The results have shown that: a wide range and strong southerly jet is not only a strong water vapor belt, but also the necessary conditions for the lower front and lowlevel system to strengthen and move; the forcing of secondary circulation in the torrential rain plays an important role in the occurrence and development of process, its strength is directly related with the rainfall intensity. The level of cloud systems and whereabouts in the process of stratification state of the lower front to a certain extent determine the phase state of precipitation on the ground. Deep strong front zone, JiangHuai cyclones, lowlevel jet, and the intensity of nongeostrophic 〖WTHX〗Q〖WTBZ〗 vector are closely related with the location of precipitation band and its intensity.