<p>Planetary gear systems are widely used in a variety of rotating machinery, and their reliable operation is crucial. A comprehensive understanding of the operation of a planetary gear system and the corresponding dynamic response is important for condition monitoring and fault diagnosis. Traditionally, kinematic models have been used to characterize the response characteristics and failure mechanisms of planetary gear systems. However, the conventional kinematic model mainly expresses the gear meshing response and modulation characteristics by constructing finite-order trigonometric function series, so it cannot fully consider the common impact phenomenon in the gear meshing process, especially after the occurrence of local gear damage.</p><p>In this paper, an improved dynamic response kinematic model of planetary gear system is proposed. In the modeling, the multi-order resonance response modes of the gear and support system are considered. The impact response is modeled by using a multi-degree-of-freedom impact response function. The frequency distribution structure of the proposed model under different health states is analyzed. The characteristic frequencies of normal gear meshing impact response and faulted gear meshing impact response are extracted by resonance demodulation analysis. Compared with traditional models, the proposed model is able to represent the modulation features as well as the gear meshing induced impact features. The effectiveness of the proposed model is verified by experiments.</p>