Numerical simulation and diagnosis are applied to the heavy snow event happening during 6-7 January 2010 in North Xinjiang by using WRF model. The combination of the cold vortex near Balkhash Lake and the south moving trough from North Xinjiang, as well as the propagation and developing of the upper air jet was the key process connected with this serious blizzard. The synoptical conceptual model is set up for this heavy snow event. It is revealed through the diagnosis of temperature advection and frontogenesis function that, the mesoscale convergence in front of the topography led to the active contribution to the frontogenesis, and the vertical motion term in the frontogenesis function explained the most part of the active frontogenesis. The vertical movement due to the secondary circulation forced by the frontogenesis is the most importrant component through the frontogenesis secondary ciruculation diagnosis. Due to the topography effect the cold air was depositing before the mountain, and the front split into upper level part and lower part, and the change in the structure of front has obvious impact on the microphysical process of precipitation. The relative light precipitation happening in the daytime of 6 January 2010 is closely connected with the warm flow ascending along the topography and the stratus cloud in the upper level. After 20:00 BT 6 January, the warm advection was strengthened with distinct frontogenesis, the seeder feeder mechanism was formed by the split front structure, and the snowfall intensified clearly due to this more efficient microphysical process.