This paper applies the Seismic Hazard Analysis method for the cities of China to research on the probability of earthquake occurrence in the Daduhe drainage area,where the cascade dam system is located.This research is based on the potential seismic source scheme of the Seismic Ground Motion Parameter Zonation Map of China (2001),and uses Poisson distribution as an earthquake occurrence model.Earthquake magnitude obeys truncated exponential distribution.The spatial distribution function of the potential seismic source zone is taken as the first-class spatial probability distribution,and the homogeneous probability distribution in the potential seismic source zone as the second-class spatial probability distribution.Considering the seismic intensity attenuation relationship of western China,we compute the occurrence probability of an earthquake around magnitude 6.0 (5.5～6.5),7.0 (6.5～7.5) and over 7.5 in the Daduhe drainage area,where 22 series cascade dams will be built.The results can be used for hydropower plant planning,hydropower dam site selection and seismic fortification.