<p>This study selected poly (1, 4-cyclohexanedimethanol isosorbide terephthalate-co-ethylene terephthalate), whose abbreviation is PCIC, as the matrix and mainly explored the influence of antioxidant types and addition amounts on the optical properties of PC_30%IC. Through comprehensive characterization methods such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and transmittance testing, the structure, morphology, thermal and optical properties of the synthesized composites were investigated. It was found that triphenyl phosphite (TPPi) had a better color protection effect on ISB. The performance of PC_30%IC with different TPPi addition ratios was studied. The results showed that TPPi itself did not participate in the reaction, so there were no obviously characteristic peaks in the infrared and nuclear magnetic resonance test results of the product. However, TPPi could appropriately increase the molecular weight of the copolymer, and the T_g and tensile properties of the copolymer also got a slight improvement. TGA curves showed that TPPi had little effect on the Td_5% of the copolymer, but its Td_max has been increased. Moreover, the addition of TPPi could inhibit the cross-linking reaction or carbonization which could aslo reduce the residual mass. More importantly, TPPi could prevent the occurrence of oxidation reactions by capturing free radicals and decomposing peroxides, thereby reducing the formation of chromophores. However, this effect was limited. When the addition amount of TPPi reached 0.005 of the total molar mass of the alcohol, phase separation occurred, which instead reduced the transmittance. When the content of TPPi was 0.003, the ultraviolet transmittance of the film was the best, reaching 90.94%, with a b* value of 1.25.</p> Graphical abstract <p></p>