Firefighting helicopters find their wide application in extinguishing fires in forests, high-rise buildings, hazardous material sites, and other fire-prone areas due to their advantages of high maneuverability, large payload, and long endurance. In view of an prevention of safety accidents brought about by structural issues, it is necessary to conduct a static analysis of the external water cannon system structure so as to ensure that the strength and stiffness of the designed external water tank structure can meet airworthiness standards. Firstly, a three-dimensional model has thus been established of an external water tank and connectors for fire helicopters by using SolidWorks software, with appropriate simplifications made. Subsequently, a static analysis has been carried out on the water tank and its various connectors by using the finite element analysis software. The simulation results show that the water tank and connector structure of the designed high-pressure water cannon system is characterized with good static characteristics, whcih meet airworthiness requirements, thus ensuring the normal operation and performance of the system.