Abstract: The image morphology was introduced to detect the initial welding position of straight welding seam.The straight seam image was acquired by using a small CCD camera.The erosion edge detection algorithm was used to process the image,which could maintain the key information and eliminate other interference.Finally the initial welding position was obtained by filter with directional liner structure elements and Hough transformation.The whole processing is very intuitionistic,simple and fast.In addition,it's higher self-adaptability,higher process accuracy and stronger robustness.This research can meet the need of practical work,and lay a good foundation for the guidance of initial welding position.