The reasons of sandstorm occurring frequently in spring in Hexi corridor were analyzed .we found special geographical locadon .particular topography and physiognomy and arid climatic background are the main reasons.     The number of sandstorm occurring in Hexi corridor has decreased since 1955 in general ,most in 1970 s'.least in 1990 s'.The results show that the occurring of sandstorm in Hexi corridor connects with winter monsoon of East Asia .and has吨h correlation with SST of Middle East Pacific in prophase autumn and winter.  When the SST was higher .the winter monsoon of East Asia would be weaker .the number of sand storm occurring in Hexi corridor would be less than usual. On the contrary .it would be more.