Abstract: The welding bead shape is crucial for welding quality.Three-dimensional shape of the welding pool contain much information about quality.Thus, shape from shading technique was taken to reconstruct the three dimension shape of welding pool. Welding reflection map was established and was solved by using linear approximation, from which the depth iteration equation was obtained. It then presented the improved measure for this algorithm based on Kalman filter.Finally, the experiment validate that this algorithm is fast and effective.