A conventional local calibration device used in computer is developed for calibrating thermo resistors' dynamical characteristics. The relationship between the temperature response of the surrounding temperature step changes and that of the loop current step heating is proved. Then, a data processing method is found in obtaining the response time constant. In lubrication oil and wind tunnel the LCSR and the surrounding temperature step changes are tested and compared. The result shows that the error of the time constant obtained by using this method is less than 5%. And the time constants of thermo resistor and its shell obtained respectively can be further used to determine the main factors affecting the response speed.