In order to meet the requirements of aircraft skin assembly quality, it is necessary to eliminate step differences around the seam of the skin. The skin seam location and step difference measurement before grinding are the key steps to determine the grinding accuracy. This paper proposes a point clouds processing algorithm of seam location and step difference measurement for grinding trajectory generation of the curved components. First, extract the boundary features of the preprocessed workpiece point clouds, and divide the point clouds into different regions; Second, recognize the boundary feature points, and construct the boundary line by fitting the boundary points; Finally, calculate the step difference based on the boundary line of both sides and generate the solution for grinding track generation based on the seam boundary position and the step difference. We use the line structured light based vision measurement platform to verify the proposed algorithm, and the results show that the measurement system and algorithm can achieve the seam boundary location of curved components accurately. The research work in this paper is extendable to applications in the machining of curved workpieces.