The present invention relates to welding sensing technology, and is method of realizing circular laser trace based on object lens rotation. There are rotary lens combination to eliminate aberration, fixed driving motor and laser diode with installation center distance equal to the radius of the circular trace to be obtained and equal to the distance between the driving motor and the main optical axis of the rotary lens. The motor rotates the lens, the laser diode emits laser and the rotating lens forms the scanning circular laser trace in the focus of the lens and on the surface of the welded parts. The present invention has no structural light splitting effect and forms circular laser trace with high definition and high precision, and the lens manufacturing process has spherical aberration eliminated. The present invention is suitable for locating weld seam, welded part shape measurement and weld seam tracking, as well as the depth and width measurement of weld seam.