Abstract: In the process of the diamond coating deposition of hot filament chemical vapor deposition(HFCVD),the precise control of temperature distribution,especially the temperature of substrate is one of the main problems affect the quality of diamond film. The paper proposes a temperature compensating device to improve the temperature distribution based on HF-650. Arranging reflective plates on and surrounding the substrate improves the distribution of temperature by thermal reflection. Simulation by Fluent and test by improved device will be used to verify the improvement. It is shown that the compensating device can uniform the temperature distribution of HFCVD,reducing temperature fluctuate from 9.3% to 3.0%,which has been proved by practice. With the device,high quality diamond film that I_D/I_G=4.33 has been prepared,which is positive for diamond deposition.