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Sanddust storms in Gansu Province occurred most frequently in summer. The summer sanddust storms concentrated around Minqin, Dingxin and Jinta. The weather patterns for severe sanddust storms in summer in Gansu Province are analyzed. The results show that upper troughs and shear lines and hot lows are main synoptic systems that result in summer sanddust storms. Spring sanddust stor ms are mostly induced by largescale synoptic systems. Before the occurrence of summer sanddust storms, the upperlevel jet currents are not apparent. The sudden wind speed increase of the jet stream happens almost at the same time with a sanddust storm, and that is one of difficulties in summer sanddust storm prediction. The helicity field 8 to 12 hours before sanddust storm occurring is a good indicator in forecasting sanddust storms. The larger the helicity is, the severer the sanddust storm is. But when a sanddust storm and severe precipitation occur concurrently, the value of helicity in the sanddust storm region is obviously less than that in the severe precipitation region.