Based on the reanalysis data from National Centers for Environmental Prediction (NCEP) and the ground area automatic station data and the data from Meteorological Information Comprehensive Analysis and Processing System (MICAPS), the characteristics of four winter heavy precipitation processes in Yunnan were studied. Then based on the model of Hybrid Single-Particle Lagrangian Intergrated Trajectory (HYSPLIT), the main paths affecting the winter heavy precipitation in Yunnan and the water vapor contributions from different sources were simulated. Results show that process 1, influenced by the south trough, the shear line and the surface cold front, is the strongest process of provincial heavy precipitation in winter of Yunnan in recent years. Processes 2 to 4 are only affected by the south trough and the surface cold front or the quasi-stationary front. The average daily water vapor flux of the whole layer is positively correlated with the number of rainstorm stations. When precipitation occurs, water vapor enters the west and south boundaries of the lower troposphere to the upper troposphere. Process 1 has the largest water vapor budget and range of heavy precipitation. In process 2 and 3, the input of water vapor is large, but the output of water vapor is large at the same time, so the budget and range of heavy precipitation is medium. Process 4 has the smallest water vapor budget and range of heavy precipitation. 41% of the water vapor at 500 hPa above Yunnan rainstorm area comes from Indian Ocean, 55% of the water vapor at 500 hPa above Yunnan rainstorm area comes from Atlantic Ocean, and 4% of the water vapor comes from western Pacific Ocean. 26% of the water vapor at 700 hPa above Yunnan rainstorm area comes from the western Pacific, 59% of the water vapor comes from the Indian Ocean, and 15% of the water vapor is from the Atlantic Ocean. 17% of the water vapor at 100 meters above the surface comes from the western Pacific Ocean and 83% of the water vapor comes from the Indian Ocean. Comparing the water vapor flux and precipitation of the four processes, the water vapor from the Indian Ocean plays an important role in precipitation.