A device for measuring thermal diffusivity based on laser flash method is developed. The furnace is vacuum pumped by mechanical pump and molecular pump, then heated. The measured sample is stimulated by high-power pulsed laser instrument. The temperature of the sample increases on the laser irradiation surface, and the heat begins to transmit to the other side. The infrared detector records the temperature rise process in real time and converts it into an amplifier after amplification. The voltage signal is input to the acquisition card and communicates with the computer software. The self-compiled measurement software calculates and processes the data in real time, and then gets the thermal diffusivity value of the sample. The system was used to test the standard sample in the temperature range of 300 ~1300 C. The repeatability of the measurement was less than 0.85%.