In this study, the deformation mechanism of Prestressed Steel Cylinder Concrete Pipe(PCCP) under complex loads is analysed by numerical simulation. The influence of the change in the number of broken wires along the pipe direction and the different transverse fracture locations of the pipe on the deformation and bearing capacity of the PCCP pipe under complex loads is mainly considered, and the accuracy of the simulation method is verified by comparing with the in-situ test data. The results show that under the combined effect of complex loads, the number of broken wires increases, the circumferential strain of the concrete in the core of the pipe increases, and the broken wires lead to more significant elliptical deformation of the pipe and affect the bearing capacity of the pipe. When the prestressing wire breaks at the top of the pipe, the vertical deformation of the pipe increases significantly compared with other positions (e.g., 45° or 135° at the side of the pipe), and the load-bearing capacity of the pipe is weakened. This research result enriches the theoretical system of the deformation mechanism of PCCP pipe and provides a treasure reference for engineering practice.