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The supercapacitor, because of its advantages of high specific power, quick charging or discharging with high current rates, and long cycle life, is an interesting choice for energy storage for applications where high power is needed for only a few seconds, such as pulse-power supply systems. Based on the use of supercapacitors all around the world, more and more attention is focused on the effects of temperature on their performance metrics such as capacitance, internal resistance, and efficiency. To predict the terminal voltage of supercapacitors at different temperatures, a three-branch RC equivalent circuit model is improved in this paper, and it can predict the terminal voltage up to 5 to 10 min after completion of charging or discharging. Initially, a typical three-branch RC equivalent circuit model without temperature parameter is used to simulate the pulse charging and discharging behavior of a specific commercial supercapacitor. Next, with the pulse charging and discharging experiment results under -40°C, -20°C, 0°C, and 20°C, all parameters in the circuit model are reset to a function of temperature, and the temperature dependence of parameters is discussed in detail and determined numerically. Finally, for the purpose of validating the correctness and the accuracy of the improved model, compared study of simulation results and experiment curves is done. Comparison results show that the fitting accuracy of the improved equivalent circuit model is satisfied in pulse charging and discharging at different temperature.