Using the routine observational data, FY-2C satellite TBB and NCEP reanalysis data, the heavy snow occurred on Nov.10-12, 2009 in Shaanxi province is analyzed, the results show that the short-wave trough at 500 hPa and the shear line at 700 hPa and 850 hPa are its mainly influencing systems, and snowstorm is directly caused by meso-scale convective clouds. The mesoscale systems and cold centre of TBB corresponding to the heavy rain center can be clearly seen from the stream field after filtering. The snowstorm occurred in the east of positive ζ_MPV1 centre, namely in the negative ζ_MPV2 area. The atmosphere baroclinity enhances because of strong vertical wind shear caused by ascending warm south wind and cold north wind and because of the presence of ▽θ_se. Long axis of positive vertical helicity is always consistent with low-level shear and lies in the east of it.