Abstract: Based on the fuzzy membership degree theory, fuzzy rotation angle of joint is provided in terms of its flexible displacement. The element stiffness matrix of space flexible beam and the relationship between fuzzy rotation and spring stiffness were derived based on the concept of fuzzy rotation angle of joint. The axial stiffness of truss member was presented considering the effect of connection slippage. Program of space flexible joint model with the function of analyzing slippage of joints (SFJS) was developed in MATLAB. SFJS is used to obtain the axial force of legs and diagonals of JJ3-type transmission line steel tower. The numerical results and full-scale test results matched fairly well. By means of the space flexible joint model with slippage, the internal force distribution in the bar of transmission line steel tower can be solved more accurately than the traditional space frame model. The SFJS provides theoretical foundation for design, calculation and protection of transmission line steel tower located in mining areas. Compared with the traditional modal of space truss, SFJS can calculate more accurately the internal force of truss members induced by the deformation of foundation