For the purpose of investigating the strengthening effectiveness of GFRP on concrete filled steel tube structure under combined seismic loading and comparing with CFRP ones, numerical simulations of quasi-static test are developed by using ABAQUS. The establishment of finite element model is tested to be feasible by comparing the numerical load-displacement hysteretic curves and their skeleton curves with the experimental ones. Further studies are carried out through changing models’ FRP (GFRP/CFRP) thickness, axial compression ratio and cross sectional steel ratio. Simulation results show that specimens with thicker FRP (GFRP/CFRP) equip better energy dissipation capacity and higher bearing capacity. In elastic-plastic stage the stiffness of specimen degradation becomes more serious as axial compression increases. Energy dissipation capacity is enhanced as cross sectional steel ratio increases.