The invention discloses a transient temperature measuring system for a diesel engine piston and a measuring method thereof. The system comprises a data acquiring, amplifying and transmitting device, a signal receiving device, a computer, a temperature measuring screw and a compensating lead, wherein the temperature measuring screw is connected with the data acquiring, amplifying and transmitting device through the compensating lead; the data acquiring, amplifying and transmitting device is connected with the signal receiving device through a wireless transmission signal; and the upper end face of the temperature measuring screw is provided with a film thermocouple. The method comprises the following steps of: making a mask and a mask clamp; making a temperature measuring screw; installing; and measuring. According to the measuring system, temperature is measured by using an advanced film thermocouple preparation technology, so that short dynamic response time is ensured, high temperature measuring accuracy is realized, and continuous measurement can be performed. Meanwhile, a small screw structure is adopted, and a sensor is easy to manufacture and can be placed on the piston easily; and the transient temperature measuring system is simple in structure, is convenient to replace, and can be produced in a standard way. Due to the adoption of the transient temperature measuring system and the measuring method thereof, the problems of temperature testing of the diesel engine piston in a severe working environment and the problem of lead connection of the film thermocouple are solved.