Improper emergency response in the event of engine failure for large UAVs can lead to crashes and cause serious economic losses. However, there are few experts who study the fault-tolerant control law for UAVs with dual engines in the past decade. Therefore, this paper studies fault-tolerant control technology for UAVs with full engine failure. Firstly, we calculate the residual energy of the UAV with full engine failure and analyze the unpowered return capability. Secondly, the mechanism of recovery control for the UAV with full engine failure is studied and the route for the autonomous forced landing is planned. Then, we studied the fault-tolerant control technology and reconstructed the control law for the UAV with full engine failure. Finally, fault simulation is carried out to verify the fault reconstruction and recovery control method, using digital virtual flight simulation methods by setting up a scenario of UAV with full engine failure,. The simulation results show that the fault-tolerant control law studied in this article can achieve autonomous return forced landing control for faulty UAVs with full engine failure, providing a basis for fault-tolerant control and autonomous return forced landing of UAVs with engine failure.