Abstract: An active vision sensing system is founded.The low power laser is an active light-source which is projected laser on to the specialized grating, deformed laser stripes are formed on the surface of the welding pool, narrow band filter and neutral density filter are mounted on CCD for acquiring pool images at real time on the other side of system.When the projected angle and acquired angle are selected properly, it can avoid the interference of arc to make the pool image better, and deformed laser stripes can be gathered. The characters of pool images are analyzed, deformed laser stripes reflect the information of the concave or convex of the pool.Both the pool boundary and the deformed stripes edges are extracted successfully.The geometry parameters of pool obtained by demarcation and calculation lay the foundation for real time detection of the 3-D information of welding pool surface.