Abstract: By using routine observation and NCEP reanalysis data,the characteristic of the heavy precipitation events in Yunnan in August 2425,2013 has been analyzed.The results show that the large scale heavy rainfall can be caused by the movement of the westward typhoon and the invasion of the dry and cold air in middle troposphere.Stable and sustained vapor transportation and vapor convergence are important factors to heavy rainfall.Convective uplift which is caused by dry and cold air moving forward south and penetrating to lower level will enhance the convection,which would help the occurrence of rainstorm.On the one hand,two conditions that cold air meets on east side jet in northeast Yunnan for long time can cause long time heavy rainfall in northeast Yunnan.On the other hand,the intersection time and region of tongue dry air and tropical depression just correspond to the time and region of rainstorm in southwest of Yunnan.The front of dry cold air is a good correlation of rainstorm region.heavy rain occurring at the region where the back part of dry air joined with humid air mass.The area of heavy rain has better corresponding relation with the region where MPV is unusual.