In the paper, five different antioxidants were adopted to improve the antioxidant capacity and to prevent color change of the semi-aromatic polyamide PA6T/66 caused by oxidation in the application. Thermal gravimetric analysis (TGA) showed that the initial decomposition temperatures of the modified plastics in air atmosphere were elevated effectively. Thermal oxidation of the suppressed films and mechanical testing samples were performed at 170 ℃ for 8h. The differential scanning calorimetry(DSC) results suggested that the melting points of the samples were all at about 310 ℃, but the crystallization temperature increased after thermal oxidation. Decrease after initial growth of the intrinsic viscosity suggested that there existed a competition between crosslinking and degradation in PA6T/66. The antioxidants inhibited the degradation, and resulted in a maintained high intrinsic viscosity of PA6T/66. UV-visible (UV-Vis) spectroscopy showed the chromophore absorbance at 325nm increased with increasing of oxidation time, which slowed down after adding antioxidants. No obvious change in mechanical properties was detected before and after oxidation since oxidation only happened on the surface of the samples. Comprehensive tests results suggested that the antioxidation of PA6T/66 was successfully improved with the present of antioxidants. The antioxidant effect of the organic compound was superior to the organic antioxidants alone, and the effect of inorganic and organic antioxidants compound effect showed little different.