Abstract:  As one of the key components in robot, the harmonic reducer directly affects the reliability and service life of the whole system. It’s necessary to establish a more precise mechanism model to explain its complicated and unique vibration features. A new methodology for harmonic drive modeling is proposed based on the lumped-parameter method and then the coupled vibration mechanism is revealed by frequency spectrum analysis. Combined with the geometric structure characteristics of the parts, the equivalent stiffness between the interacting elements is qualitatively analyzed; The dynamic differential equations of the harmonic reducer with three degrees of freedom in the torsion direction are established, and the mapping relationship between the dynamic stiffness characteristics caused by the harmonic gear meshing and the vibration response characteristics is analyzed. Through the mechanism and simulation analysis, the frequency distribution law of the vibration response of the harmonic reducer is revealed. It’s proved in the experimental signal that this harmonic drive model can replicate many features in actual vibration response