In view of the features of panel position of shadow-mask plasma display pare (SMPDP), two methods of precision positioning are brought forward: image positioning method and grating positioning method. The compound control system for precision positioning is set up using two kinds of the positioning technique, in which the image positioning method is used as the coarse alignment and the grating positioning method is used as the fine alignment. By using the two-step alignment, the high alignment accuracy and quick alignment speed are obtained in the big long positioning range. The algorithms such as fast image edge detection, character extraction, precision gratings detection and precise driving strategy are adopted to effectively improve positioning accuracy and reliability of the device. The experimental result shows the two-step alignment can perform positioning accuracy of ±0.15 μm in the working range of 50 mm.