Landing gears are one of the key components for large or middle unmanned aerial vehicles,and their working performances directly affect flying security and aircraft taking-off and landing performance.Thus,it is meaningful to study the retraction system.Based on CATIA and ADAMS software platforms,a virtual model of landing gear retraction system is built for performance test,and then dynamic simulation is carried out.Afterwards,a test system for landing gear retraction is established,and the test data are compared with the results acquired from dynamics simulation.The main factors which affect the dynamic performance of retractable landing gear are analyzed emphatically.The simulation results show that aerodynamic load has an impact on retraction time,the mass force affects extension process,and the oil hole size of hydraulic actuator has an effect on both retraction time and extension time. Landing gears are one of the key components for large or middle unmanned aerial vehicles, and their working images directly affect flying security and aircraft taking-off and landing performance .hus, it is meaningful to study the retraction system. Based on CATIA and ADAMS software platforms, a virtual model of landing gear retraction system is built for performance test, and then dynamic simulation is carried out. Afterwards, a test system for landing gear retraction is established, and the test data are compared with the results acquired from dynamics simulation. The main factors which affect the dynamic performance of retractable landing gear are analyzed emphatically. The simulation results show that aerodynamic load has an impact on retraction time, the mass force events extension process, and the oil hole size of hydraulic actuator has an effect on both retraction time and extension time.