Abstract: In order to improve the endurance time and load capacity of the emergency rescue UAV during operation, the ' X ' type four-rotor heavy-duty emergency rescue UAV is taken as the research object. Using SolidWorks software, according to the design parameters, the frame, offset mechanism, throwing device and lifting device are designed according to the design parameters, and the selection and design of the relevant parts of the transmission system are completed. The research results show that the continuous flight time of the designed UAV can reach 4 h, the maximum load capacity is 160 kg, and the basic functions such as pitch, roll, yaw, vertical take-off and landing, and long-distance wireless control can be realized, which provides a reference for the structural design of emergency rescue UAV.