The stress state of joints is the key to the mechanical performance of the space structure. In this paper the constant amplitude fatigue performance of the pin in space structure was investigated. The fatigue numerical simulation of 32 theoretical models with 5 factors was carried out on the basis of similar numerical models and nCode Designlife analysis software.The S-N curve was obtained and the fatigue life calculation formula was established. The analysis results indicate that: Under the symmetrical cyclic loading (R=-1), the hot spot stress of the pin locates at the contact surface of the pin with the interface of the outer and inter ear plates, and the nominal allowable stress amplitude corresponding to 2×106 cycles is 94.42 MPa. The constant amplitude fatigue performance of the pin is negatively correlated with the three parameters, the pin hole clearance, the thickness of the ear plate, and the distance between the ear plates, while positively correlated with the pin diameter and the yield strength of the pin material. The ranking of the sensitivity of the factors affecting the constant amplitude fatigue performance of the pin is: the material of pin→the clearance of pin hole→the space between ear plates→the diameter of pin→the thickness of ear plate.