According to the conventional meteorological observation over the period 1981-2000 and NCEP/NCAR reanalysis data, coupled with synthetic analysis and power diagnostic analysis method, the paper illustrates the spatial distribution of coldair snowstorm and noncoldair snowstorm, atmospheric circulation, vapor transportation, stability and vertical motion and does comparative analysis. The results indicate that coldair snowstorms are meso and microscale snowfalls which occur in the northwest air flow behind trough, while the noncoldair snowstorms tend to occur in southwest air flow in front of trough, usually largescale snowfalls. Coldair snowstorms have distinct local characteristics, resulting from the response of strong cold air to the physical condition of underlying surface. In addition, this paper proposes that the unstability of atmospheric boundary caused by the strong interaction of cold and warm waters of the Bohai Sea is the nature of coldair snowfalls, and the snowfalls occurring in such unstable stratification of boundary layer is the concept of coldair snowfalls.