To evaluate the landing response of the large civil aircraft in the conceptual design phase , a method for simulating aircraft landing is given.The model for the shock absorber is investigated.The flexible airframe model is established using finite element model ( FEM ) to analyze its modes.Then , the whole aircraft model with flexible airframe is made for the multibody simulation.Tail-down , two-point , three-point and sideslip landing scenarios are studied.The influence on the landing performance considering mode superposition of the flexible airframe is analyzed.Both longitudinal and spanwise positions of the main landing gear are changed to research the influence on the landing performance.Results show that the method is feasible.The shock absorber axial force of the main landing gear with the flexible airframe is smaller than that of rigid airframe.The number of mode superposition and the position of main landing gear can influence the landing response. To evaluate the landing response of the large civil aircraft in the conceptual design phase, a method for simulating aircraft landing is given. The model for the shock absorber is investigated. Flexible airframe model is established using finite element model (FEM) to analyze its modes.Then, the whole aircraft model with flexible airframe is made for the multibody simulation. Tail-down, two-point, three-point and sideslip landing scenarios are studied. influence on the landing performance considering mode superposition of the flexible airframe is analyzed.Both longitudinal and spanwise positions of the main landing gear are changed to research the influence on the landing performance. Results show that the method is feasible. shock absorber axial force of the main landing gear with the flexible airframe is smaller than that of rigid airframe. The number of mode superposition and the position of main landing gear can influence the landing response.