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Structural evolutions of cellulose triacetate (CTA) film during uniaxial stretching process at different temperatures were studied by in-situ synchrotron radiation wide-angle X-ray scattering (WAXS) combined with dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The results show that four temperature regions can be divided for the CTA film stretching, in which different structural evolutions and deformation mechanisms will be observed. The structural evolutions of CTA film at temperatures between 60 and 125 °C (region I) are seriously influenced by the absorbed moisture, resulting in a large variation of the crystallinity ( χ c ). At temperatures around T g (195 °C), stretch-induced orientations for crystal can be achieved more easily although χ c and crystal size have no large change compared with the flexible-chain semi-crystalline polymers like polyethylene. Interestingly, the CTA film presents various deformation mechanisms including the elongation of amorphous and slipping, formation, destruction and recrystallization of crystals during stretching at different temperatures, which are often observed for the flexible-chain semi-crystalline polymers. These results can provide valuable guidance for the hot-stretching processing and application of CTA retardation film. Image 1 • The structural evolutions of CTA film during stretching were studied by in-situ WAXS. • Four temperature regions with different structural evolutions were observed. • The structural evolution is affected by absorbed moisture at low temperature. • Stretch-induced orientation can be achieved more easily at temperatures around T g. [ABSTRACT FROM AUTHOR]