Abstract: In order to improve the strength of composite T-joint, effects of adhesive, filler and Z-pin on enhancing strength of composite T-joint were studied. Same size samples with two different adhesives, two different fillers and Z-pinned and Un-pinned composite T-joints were designed, Tensile tests were performed and then ultimate displacement and ultimate strength were obtained and compared. Damage evolution of T-joints was analyzed. It is shown that the ultimate displacement and strength of J299 adhesive composite T-joint are 57.8% and 64.7% higher than that of J116B joint, and the ultimate displacement and strength of ZXC195 enhanced core composite T-joint are 51.7% and 30.3% higher than that of unidirectional core joint, and Z-pin increases the ultimate displacement and strength of composite T-joint by 190.8% and 31.9%. These three structure parameters can only alter the ultimate strength and displacement of composite T-joint, but the structure stiffness keeps unchanged. Adhesive property has the largest effect on the ultimate strength, while Z-pin has the largest effect on the ultimate displacement.