Thermostat, as the automatic temperature control device of the cooling system of the engine, has an important effect on the engine. In order to solve the problems in traditional mechanical thermostat performance detection, such as data deficiency, low measuring accuracy, high security risk, and inconvenience to operate. We find a non-contact way to get the real time lift of the thermostat based on laser ranging technology, and get the synchronous temperature by the temperature sensor. In this way, we can obtain the complete data of the thermostat. This method is an accurate, safe, convenient, and non-contact way, temperature measurement accuracy is 0.1 °C, and lift measurement accuracy is 1 mm. We setup a thermostat detection system and verify it by experiments with the Jiefang J6 thermostat. The result shows this system can detect the performance of thermostat accurately and efficiently, such as temperature stability, performance consistency, and fault diagnosis criterion. It is applicable to ordinary engine maintenance as well as educational practices.