Abstract: The stress simulation results show that the maximum stress on the weld of static pressure cavity is 133.62 MPa when the airborne radar is working, which does not meet the strength requirement. Structure optimization for the static pressure cavity is needed. Building arch structure and local reinforce are two common structure optimization schemes. After comparing these two schemes, the scheme of adding a stiffener on each of the front and back sides of the static pressure cavity is adopted. When solving the optimal width and thickness of the stiffener with the aid of ANSYS Workbench, an output parameter directly describing the optimization effect is created according to the relationship between the strength requirements of different locations. And the parameter is used to define the model of the multipurpose optimization. After optimization, the maximum stress on the weld of static pressure cavity is 82.821 MPa and the maximum stress in other locations is 59.921 MPa, both of which meet the strength requirement. Different locations usually have different strength requirements, according to which a new output parameter is created to solve the optimization model. This method has reference value for similar problems.