For the problem of precision deficiency of the analysis model caused by nonlinear factors of the joint parts in the 150 mm mirror, the equivalent linearized model and the model updating method were presented. First, the experimental modal parameters of the 150 mm mirror within 800 Hz were tested and obtained under the actual assembly and boundary conditions. Then, according to the dynamic characteristics of the interface joints, the equivalent finite element model of the mirror was classified as the connection model of fixed parts, the screw model and the equivalent gap model of the clamping parts, which were modeled by beam elements, rigid elements and spring elements. Finally, taking the measured experimental data including natural frequencies and modal shapes as the objective function, the dynamic model of the 150 mm mirror was corrected by using optimization method. At the same time, the modified model was divided into two parts according to the characteristics of the joints by adopting the idea of hierarchical and step-by-step modification to improve the efficiency of the correction process. The results indicate that the average error of natural frequencies within 800 Hz after model updating is 1.6%, and the minimum value of modal assurance criterion is greater than 0.8, which improves the accuracy of the dynamic model for the reflective mirror. And the equivalent linearized model is also verified.