A kind of C-shaped glass-fiber-reinforced polymer (GFRP) connector for panels was proposed and experimentally investigated in this study. The connector was extruded into C-shape with anchorage rebars at ends. The C-shaped GFRP connector has large stiffness and bearing capacity, allowing sufficient connection between panels with high thickness insulation layers. Shear, tensile, and compression tests were conducted to quantify the performance of connectors under different loading conditions. The length and loading direction of the connectors were main parameters investigated by shear testing. As the connector’s length increased, the failure mode of the connector with strong-axis bending tended to be anchorage failure instead of connector failure. The failure mode of the connector with weak-axis bending tended to be connector failure in the 60–300 mm length range. Equations were derived to predict the damage mode of the connector system. The results from tensile testing and compression testing revealed an anchor failure mode related to the anchorage rebars and concrete. Such C-shaped GFRP connector design was also capable of resisting the force and displacement of panels with a thick insulation layer up to 300 mm.