Abstract: In order to analyze the structure and temperature-regulating performance of Outlast viscose fiber, the structure of Outlast viscose fiber was observed respectively by FTIR spectra, X-ray diffraction and scanning electron microscope, and the temperature-regulating performance of Outlast viscose fiber was investigated by differential scanning calorimeter, thermal gravimeter analysis and cooling test. The results show that the structure of Outlast viscose fiber is similar to that of normal viscose fiber. Both the melting peak and crystallization peak of Outlast rayon fiber are double peak, and the phase change temperature range is applicable and the phase change enthalpy is high. The decomposition temperature of Outlast viscose fiber is about 280~320℃. The cooling velocity of Outlast viscose fiber decreases exponentially as the time increases, and the temperature-regulating ability of Outlast viscose fiber is obviously better than that of normal viscose fiber.