The registering precision is one of the most important specifications in printing press. Many factors that may influence the registering precision including the construction of the printing press in design, the assembly precision in manufacturing stage, adjustment in process of operation, the wear and tear of the machine when it is in use, crawl of blanket and extension of sheet are all considered comprehensively. The mathematical models are built up to describe the register error of press. The algorithm of accuracy and precision of sheet-feeding and sheet-transferring is introduced. With the aid of image technology, the coordinates of marks can be obtained automatically, and the registering accuracy and precision can also be calculated.