There are some structural parameter errors and some material property errors between the Finite Element Model (FEM) and the Real Structure of Antenna (RSA). Because of these errors, the FEM can not realistically reflect the RSA performance under various loads. In this paper, a parameter compound optimization method is proposed for updating the submillimeter-wave antenna finite element model. The method consists of three steps. Firstly, the parametric finite element model of the antenna is created, and the sensitivity analysis is carried out. Secondly, establish the objective function. The performance of the imaginary RSA is chosen as the optimization object, and the high sensitivity parameters act as the optimization variables. The performance of the FEM before optimization is chosen as the initial value. Thirdly, the compound optimization is carried out based on the zero-order method and the first-order method. In order to verify the feasibility of the parameter compound optimization method of the FEM updating, we take the 1.2 meter submillimeter-wave antenna as research object and optimize it respectively under different loads for various material property parameters. The results show that the performance of the FEM is identical to that of the imaginary RSA after the parameter compound optimization. Thus, the feasibility of this method has been proven. Besides, based on the updating model of the antenna, the deformation regularities are analyzed under gravity load. Moreover, the method could also be applied to update the large aperture submillimeter-wave antenna finite element model.