With the rapid development of UAVs (unmanned aerial vehicles) toward longer endurance, higher payload capacity, and miniaturization, the demand for lightweight design and structural simplification of landing gears has become increasingly urgent. A landing gear retraction-extension system controlled by a single actuator for both retraction/extension and locking operations was designed. The system integrates the retraction/extension driving and locking functions via a single actuator, which effectively reduces the structural weight and complexity of the landing gear.Three-dimensional parametric modeling and DMU (digital mock-up) kinematic simulation were performed using CATIA software to verify the feasibility of the retraction-extension structure and the interference characteristics of the mechanism. A multibody dynamics model was established based on the LMS Virtual Lab Motion platform to analyze the load characteristics of the actuator during retraction/extension and to evaluate and calculate the structural strength of the actuator. Additionally, drop-test simulation was conducted to assess the dynamic response characteristics of the landing gear system under landing impact loads. The results indicate that the system can effectively absorb impact energy and meet the specified structural strength requirements. Finally, experiments were carried out to verify the reliability of the mechanism design as well as the effectiveness of the kinematic and dynamic simulations.This study achieves effective reduction in system weight while ensuring the functional reliability of the mechanism, thereby providing an engineering reference for the lightweight design of UAV landing gears.