Abstract: It is convenient to combine the response surface model with the particle swarm optimization(PSO) and other optimization algorithms to replace the finite element model (FEM) for improving the updating efficiency and precision. Modal frequencies of a concise radar satellite were calculated by the FEM based on several sets of parameters obtained from the orthogonal design, the non-updated parameters were determined by the variance analysis, the quadratic polynomial was constructed, with its coefficients being calculated by the least squares method(LSM), and the fitness function was constructed by the differences between the results of the response surface model and the FEM, which was used to guide the particle swarm with chaos search mechanism to search for the optimal solution of the non-updated parameters to constitute the updated model. The modal frequencies of the updated model can both reproduce the modal frequencies of the benchmark model in the test range with high precision and predict those out of the test range with acceptable precision, which shows the validity of the model updating method.