Pendulum eddy current TMD as a new type of damper is often used in the control of human-induced vibration and wind-induced vibration, but seldom used in seismic engineering. And there is still a lack of effective calculation methods. In this paper, a coupling calculation method based on joint simulation is proposed to investigate the damping performance and reasonable value of mass ratio. A numerical model is established for 5-story, 10-story and 20-story steel frame structures along with five groups of pendulum eddy current TMDs with different mass ratios, which conform to the current Seismic design code for buildings and mechanical properties of pendulum eddy current TMD. A dynamic time-history analysis is performed on the numerical model by using coupling calculation method. The analysis yields a series of curves of story drift, interstory drift ratio, story shear force, and story acceleration versus mass ratio under rare earthquakes. The analysis results are compared to the results of the control model that has no pendulum eddy current TMD. The comparison shows the feasibility of the proposed coupling calculation method and that pendulum eddy current TMD can effectively reduce the seismic response of the steel frame, with a 26.5% reduction for story drift, 20.9% for interstory drift ratio, 4.3% for story shear force, and 7.3% for story acceleration of a 20-story steel frame structure when the reasonable mass ratio is recommended to be 3%.