Laser interferometry system was developed to measure unsteady gas temperature. A 16-element photo-diode array was used as the system to detect moving direction of interference fringe more sensitively. Laser interferometry has advantage of nonintrusiveness and high-response. These advantages can improve weak point of general method such as thermistor and thermocouple. In this study, unsteady air temperature was measured by using developed system. Compared with K-type thermocouple of which wire diameter is 0.014mm, this system showed a good response. Because of high response, this system is expected to measure unsteady gas temperature in industrial field.