An analysis is made of the water vapor transport characteristics of a sudden heavy rainstorm occurred in Huaping, the northwestern Yunnan Plateau, using the conventional calculation and numerical simulation method. The results show: The stable maintenance of the tropical depression in the IndoChina Peninsula and the depression in the Bay of Bengal provided a largescale environmental field for the establishment of the water vapor transport channel in the rainstorm area. There were two water vapor transport channels in the rainstorm area: the water vapor transport on the east side of the depression in the Bay of Bengal and that on the south side of subtropical high, of which the source area can be traced back to the South China Sea, the Western Pacific, the Bay of Bengal, the Arabian Sea, etc. The water vapor transport and water vapor convergence mainly came from the lower levels below 700 hPa, and the water vapor transport characteristics of 700 hPa and 850 hPa were consistent with that of the whole layer. The numerical simulation results can better reproduce the characteristics of water vapor transport in the rainstorm area, and at the same time, during the back tracking period, the middle and low water vapor transport in the storm area started above this height, and along with the occurrence of heavy rain, the water vapor transport height gradually reduced.