Abstract: By using the PSU/NCAR MM5 middle cale numerical model to simulate the heavy snow and freezing rain process from 16 to 18 in January 2011 of the Guiyang airport.The results indicate that the main system of causing to this process were the Kunming stationary front，the south branch trough and the low jet.The middle-low layer was East-North stream，the middle layer was the South-West low stream，but the South-West low jet at early stage of the freezing rain period was strong and its layer was thick，the temperature field showed to the cold-warm-cold distribution.There was temperature inversion at low layer.The humility field ‘s distribution showed that the upper layer was dry，the middle layer was wet and the law layer was dry.After snowing，the low jet showed weak and the layer was thin，the low layer was the same temperature layer，the warm layer disappeared，the humidity’s distribution showed that the low layer was wet and the upper layer was dry，and the low layer was the weak upflow.the middle layer was the downdraft，and the low layer was convergence，the middle layer was divergence.Afer snowing，the low layer changed to the weak downdraft，the middle layer changed to the upflow，and the upflow layer was thick and strong with increasing the snowfall，and the low layer was divergence，the middle layer was convergence.The analysis on the cloud microphysical process indicates that at the early stage，the cloud water content was main in cloud systems,the high value area was at 800-600 hPa.After snowing，the cloud water content was gradually dying down and disappear，the cloud ice content appeared and maintained in whole layer.