Abstract: In order to investigate the process parameters and properties of CuNiCrSi copper alloy jointed by friction stir welding, the orthogonal experimental method was used to optimize the process parameters, and the properties and material flow were studied. The results show that the welding speed is the most significant factor affecting the welding process. The experiment has got the best combination of process parameters, and the tensile strength of the weld was 491.4 MPa, which was 84.7% of the tensile strength of the base metal under these optimum welding parameters.When the welding speed is too large, there will be tunnel defects on the advancing side of the weld, and the flow of the forward material is more complicated than that of the retreating side. When the welding speed is too small, the surface will have fin.The coarse particles in the parent material area are segnagations of chromium and silicon, and the nickel is uniformly distributed in the material. The grains in the nuggest zone become smaller as the welding speed increases. Under the optimal parameters, the grain size of the nuggest zone is small and uniform, but the hardness is lower than that of the base metal. The fracture method is ductile fracture, which indicates that the material has good toughness.