Abstract: According to the disadvantages of the present detection methods of penetration, such as the low signal-to-noise ratio, the poor real-timeliness and the like, this paper proposes a laser photoelectric conversion method that the real-time detection for the DC-TIG weld penetration state under the condition of stationary and traveling weld can be realized by extracting characteristic parameters of the weld pool surface. The principle of the method was introduced and an experimental platform for the voltage signal detection was established using the DC-TIG laser photoelectric conversion method as well as the synchronous video collection of the penetration at the back, collecting the voltage signals and synchronous video images under the condition of stationary and traveling weld and analyzing the corresponding relationship between the voltage signals and the penetration state as well as the change rule of the voltage signals. Result shows that the voltages signals collected by using the laser photoelectric conversion method can reflect the DC-TIG weld penetration state well. When the weld penetration state changes from partial penetration to full penetration, the surface of the weld pool will change from convexity to concavity and the reflected laser stripes will focus quickly, causing the phenomenon of the rapid change of the voltage signals to realize the accurate recognition and extraction of the characteristic signals of the DC-TIG weld penetration.