Abstract: From March 18 to March 23，2010，a severe sand and dust storm  affected the 21 provinces over China covering nearly 2.82 million square kilometers，and impacted 270 million people. The sand dust storm is the most strongest one since 2006. By using NCEP/NCAR （2.5°×2.5°） reanalysis data，a preliminary analysis of this severe sand-dust storm was conducted in this paper based on the weather situation，the vertical and horizontal distribution characteristics of some key meteorological parameters，the dynamic and thermal conditions which induced strong upward motion，and dynamic mechanism that sand-dust was blown and raised during the dust storm. The distribution of air pollutants concentration near the ground and visibility variation were also analyzed based on the observed air pollution index[（API）] data of China and visibility data of Beijing. The sand-dust storm could be divided into two stages，the first stage was from March 18 to March 21，the second stage was from March 21 to March 23. The sand-dust storm in the former stage was stronger than that in the later stage in terms of strength and range of influence. The severe sand-dust storm was mainly caused by strong development of Mongolian cyclone. The route of the sand-dust storm was from northwest of China to north of China，then from north of China to the east and south of China. The movement route and the intensity variation of the sand-dust storm were clearly envailed by the time series data of [API] and visibility observed in Beijing. The primary sand-dust sources were from southern Mongolia，southern and eastern Xinjiang，and the west and middle of Inner Mongolia in China. With the interaction of thermal and dynamic factors（the intensive thermal advection and vortex advection），the Mongolia cyclone was developed quickly，moving torward east and then southeast. The altitude trough at 500 hPa level was gruadually deepened due to cold temperature advection and moved forward due to vortex advection. Generally saying，the Mogolia cyclone and cold front were the main dynamic factors which induce the sand-dust storm and carry out long distance transportation of dust. In this paper，some critical thermal and dynaic mechanisms were identified for the sand-dust storm that wolud be sound basic perspectives to simulate the sand-dust storm process in the next step.

Key words: sand-dust storm, Mongolia cyclone, temperature advection, vortex advection