This article makes a simulated analysis on main landing gear door of a common short-range civil aircraft under serious air condition based on finite element software Patran and Nastran, and verifies the correctness of the finite element model. Lastly, boundary constrained optimization is performed on the door according to finite element analysis result, and the door`s deformation before and after optimization was compared and analyzed. The analysis result indicates that the door`s deformation and structure stress are obviously decreased after boundary constrained optimization.