By use of the next generation mesoscale nonhydrostatic model WRF, a backflow snowstorm over North China on Nov.24-26,2004 was simulated and analyze d. The development mechanisms of backflow precipitation are analyzed with the r easonable simulation results. The results show that dynamical frontogenesis play s a very important role in the development of backflow snowstorm. The frontogene tical secondary circulation directly causes the snowstorm. Mount Tai plays a ver y important role in the case and makes the positive and minus extremes of vertic al velocity in the upslope and lee, respectively. Meanwhile it affects the dist ribution of rain water and cloud water.