Abstract: The integrally formed glass fiber reinforced polymer (GFRP) connection is the key structural component of the transmission tower's GFRP line-suspension module, requiring investigation into its capacities. Initially, two typical connections were examined experimentally, yielding mechanical properties including load-displacement curves and failure modes. Subsequently, a finite element model based on progressive damage evolution was established. Using the experimentally validated model, sensitivity analyses on the flexural capacity in relation to parameters such as the ratio of tensile strength Y_t in the direction of the fiber to shear strength S_L, the ratio of main tube diameter D to thickness T, the connection beam width B, and thickness w were conducted. Based on Hashin's failure criterion and regression analysis, an approximating equation for the connection's flexural capacity was derived, followed by a reliability analysis. The results indicate a good consistency between the experimental and the finite element analysis (FEA) results. The primary failure mode is the tension fracture of the matrix of the GFRP main tube near the connection. With increasing Y_t/S_L, the location of failure moves from the connection to the middle of the main tube gradually, showing a corresponding decrease in load-bearing capacity. The mean value and the coefficient of variation of the ratio of approximated capacity to FEA result are 1.032 and 6.80% respectively, and the flexural capacity derived for design has an assurance rate of 99.9%.