Abstract: To address the layout characteristics and weight reduction requirements of large unmanned combat aerial vehicles (UCAVs), this paper proposed a novel structural design for a weapon bay door actuation system aimed at effectively saving internal space and reducing system weight. The hydraulic drive unit of the system featured an innovative integration of a differential gear mechanism, enabling the system to perform independent or synchronized movement of the left and right bay doors according to different command inputs. Additionally, an internal emergency control hydraulic circuit was designed to enhance mission reliability. The AMESim simulation platform was used to simulate the system's motion under various operating modes. The simulation results showed that the novel weapon bay door actuation system met both functional and performance requirements, laying a solid theoretical foundation for future engineering applications.