The performance of landing gear extension/retraction system is of direct influence of safety and comfortable of aircraft. A landing gear extension/retraction system of certain domestic plane is taken as study object. To test the performance of the retraction/extension mechanism of a landing gear of a certain aircraft, the mathematic model of the retraction/extension mechanism is presented, and it's performance simulation is based on the 3D model of the landing gear and the 1D model of the hydraulic control system by LMS Imagine.Lab AMESim and LMS Virtual.Lab Rev的Motion software. The result shows that this retraction/extension mechanism with theoretical values can complete its extending-and-retracting task during a limited time. The simulation results which consider aerodynamic load are in good agreement with actual trend and can be as a design reference. Besides, with the help of the co-simulation model, the influence of the parameters of the uplock damping on the extension/retraction performance is studied, and it is suggested that the parameters of the uplock damping are prior selection during the extension/retraction optimization progress can be as reference of the optimization design.