Abstract: A numerical model from Shao Yaping is applied to the sand storm over China in March 2002, and the predictions are in good agreement with meteorological records and satellite images. A dynamical diagnose based on the data from model presents more information than real meteorology record about the mechanism of the sand storm. It is caused by the frontogenesis of cold front connected with Menggu cyclone. Large amount of available potential energy convert to dynamic energy in the baroclinic mesosphere. It results in frontogenesis. As the strong normal share of the wind, turbulent fluctuation is strengthened and the sands are raised up from the surface ground. The wind speed in the atmosphere of the low level has a horizontal share and this pushes the sands in the atmosphere aggregate, so the visibility descends. A strong sandstorm is produced.