Abstract: It is very necessary for the improvement of weld quality and the realization of robot automatic production to detect multi-pass weld profile parameters automatically.Automatic detective system of multi-pass weld profile parameters by band laser visual sensor was developed.The procedure of image process is as follows: smoothing, center recognition by longitudinal grey gradient, twice slope smooth process, and multiple peaks search by laser seam image analysis.It is very important for seam tracking, arc length control and torch attitude adjustment to obtain four character points of weld seam profile.And the recognition results agree with the experimental results.