In order to mark the target image on an arbitrary curved surface with high quality, it is necessary to convert the typesetted 2-D data into 3-D data so that the processing trajectory data of the specific galvanometer can be formed. On the basis of a large number of experimental measurements and calculations of laser scaling, the field-prioria least square conformal map (FPLSCM) algorithm was proposed to minimize distortion of arbitrary free-form surfaces. The practical software design of laser processing system based on a 3-D galvanometer was completed. The theoretical analysis and experimental verification were carried out. A large number of calibration measurement data were obtained. The results show that, in the range of 300mm above and below the z axis, this algorithm can effectively control the calibration distortion caused by the difference between the height and the shape of the surface to be machined at about 1%. And good processing results have been obtained on all kinds of 3-D curved surfaces. This research successfully accomplishes various surface processing tasks on free 3-D curved surface by using dynamic focusing technology. The distortion is effectively reduced by optimization algorithm.