Taking the wind turbine planetary transmission system as the research object, in order to reveal the deformation characteristics of the ring gear, the ring gear was divided into multiple sections of rigid gear teeth, and each twowheel tooth section was connected with a twoway torsion spring and hinge with a theoretical length of zero. The rigidflexible coupling dynamic model of the planetary transmission system of the wind turbine was established by considering the support stiffness, the variable stiffness of the gear meshing and the flexibility of the gear ring under the planetary frame servo coordinate system. The relative motion micro displacement and the force situation of the gear ring were analyzed, and the dynamic equation was introduced by using Newtonian mechanics. Based on the model, the deformation characteristics of the gear ring were discussed under the different torsion spring stiffness, load torque, radial support stiffness and circumferential support stiffness at the constraint point. The results provide reference for the design of planetary gear transmission of wind turbines.