Abstract: Based on the Matlab software, a program for automatic identification of vapor liquid two-phase flow interface was developed. The program can obtain such characteristics as vapor liquid interface change, vapor film thickness, vapor film departure period and normal velocity. The dynamic data of bubbles on the downward facing heated grooved surface with different inclination angles and heat fluxes were processed and analyzed by this program. The results show that when the downward facing heated surface under the nucleate boiling, the vapor film thickness increases with the heat flux, and the bubble departure period decreases with the increase of the heat flux firstly and then maintains a stable value. The vapor film departure period decreases with the increase of inclination angle, and is about 0.27 s when the inclination angle is 5°. When the boiling crisis occurs, the vapor film thickness decreases rapidly, which can be used as the basis for dynamically monitoring the boiling state of heated surface.