Abstract: The paper introduced designs of hardware and software of a temperature measuring device based on PT100 platinum thermistor, and gave experimental verification. The device uses Wheatstone bridge circuit to collect resistance of PT100 platinum thermistor, and converts the resistance to voltage difference. PIC microcontroller converts the voltage difference to temperature using piecewise linear method. The experimental result showed that the temperature measuring device has high measuring accuracy and small error, and can measure internal temperature of large power equipment with PT100 platinum thermistor quickly and accurately.