Abstract: Based on understanding the influential seismic source of field, Cornell method is used to analyze the seismic hazard and to determine the seismic probability. According to the seismic damage characteristics, three limit states of storage tank failure are determined. Because of the discreteness of tank sizes, materials and seismic impact factors, Monte-Carlo method is used to calculate the failure probability and form of tank, by which the seismic risk level of atmospheric storage tank is determined. A case analysis on the seismic risk of field tankfarm is made with this method. It is considered that strengthening the management on the relatively high risk storage tank can effectively reduce the operating risk of tankfarm.