To investigate features of the autumn weather system over Gansu Provin ce in airplane artificial precipitation enhancement, statistical analysis was co nducted， based on the data of airplane artificial precipitation enhancement ope rations from 1991 to 2002. Meanwhile, discriminant model of the autumn weather s ystem of Gansu was established by utilizing the information of sounding data and the autumn weather system features. The results show that upper air circulation of the autumn precipitation in Gansu can be divided into three categories i.e. straight and fluctuant flow pattern, southwest flow pattern and northwest flow p attern. Among those patterns, the straight and fluctuant flow pattern occurred m ore frequently than other two patterns.