Four different equations are used to fit the resistance-temperature relationship for negative temperature coefficient thermistor sensor in the range of 273.15~373.15 K. In order to obtain more general results, thermistors produced by four different manufacturers are selected for experiments. The fitting results by Hoge-2 and Hoge-3 equations are more consistent with the experimental results than S-H and R-C equations. As the amount of experiment data decreases, the fitting results of Hoge-3 equation gradually deviate from the experimental results, but it has little effect on the fitting results of Hoge-2 equation. In addition, the expression of the Hoge-2 equation is simpler than that of the Hoge-3 equation, so the Hoge-2 equation is recommended as the calibration equation for thermistors fitting.