Eccentricity has a considerable influence on the seismic effect of buildings. In this study, the seismic responses of three common frame structures under the action of eccentric torque were numerically simulated. The influence of eccentric structures on the seismic performance of buildings was analyzed through three-dimensional nonlinear simulation of a six-story building model. Maximum inter-story displacement was used as the measurement standard, and fragility curves were drawn to analyze the results. The results show that if the influence of accidental eccentric torque is ignored, then the seismic performance of the steel-structure system will be overestimated, thus affecting the safety assessment results. Conversely, if the influence of accidental eccentric torque is considered using 5% mass eccentricity of the entire floor, then the seismic performance of the steel-structure system will be underestimated.