Abstract: The paper analyzed common temperature monitoring methods, pointed out that the temperature measuring method of platinum thermistor is suitable for temperature monitoring of automatic protection device of diesel locomotive, and introduced specific implementation of the method. The method calculates value of platinum thermistor according to ADC sampling value, and then calculates temperature according to relationship of platinum thermistor and temperature of measuring points. The industrial field application result shows that the method responses fast with stable feature in temperature measuring range and has no temperature drift during long running process.