Using industrial robot system for grinding surface is a higher surface processing quality effective means. In order to obtain the three-dimensional coordinates on the machined surface, this paper firstly use a monocular camera and a word to construct a set of line lasers to obtain the visual acquisition system for processing surface grinding robots the sequence laser line picture. Then according to the characteristics of laser line, using the least squares method of parabolic fitting for each picture of the center of laser lines extracted. Continuous laser line of existence, this paper puts forward the cubic b-spline curve of each picture of the algorithm generated between it and break a smooth and continuous curve. Finally, stitch the intensity information of the laser line in every picture together. It builds a complete robot coordinate for processing surface within the 3-d information pictures, by it we can make the robot trajectory and speed planned. This article applied a large number of experimental proofs, and used robot grinding surface technique above to robot grinding test, satisfy the precision requirement of experiment, the introduction of the method is practicable and effective.