The coupling dynamics model of a planar membrane structure is established by the modal synthesis method of the fixed interface. The critical conditions for the coupling vibration of the membrane structure are accurately obtained，and the coupling dynamics characteristics are analyzed. The results show that the parameters related to the fundamental frequency of the membrane structure coupling mainly include membrane prestress，frame elastic modulus，moment of inertia，aspect ratio，side length，frame cross-sectional area，frame density，membrane density，and membrane thickness. When the membrane prestress is less than the critical value，the vibration of the membrane structure is dominated by the membrane. When the membrane prestress is greater than the critical value，the membrane and the frame are coupled in vibration. At this time，the vibration characteristics of the membrane structure are jointly affected by the membrane and the frame. With the increase of the prestress of the film，the order of the coupled vibration between the membrane and the frame also increases and the order of the mode shapes will shift backward. Dimensionless analysis of the dynamic characteristics of the membrane structure is carried out，and the similarity criterion is derived between the small-size and the large-size of the membrane structures.