The offset printing machine can be divided into monochrome, two-color, four-color and multi-color printing presses according to the number of printing colors completed by one paper feeding. It can be divided into small offset printing presses, six open, four open, half open and full sheet paper printing presses according to the maximum paper size of the printer. In addition, there is a double-sided printing press that can complete two side printing at the same time by one paper feeding. According to the fountain system, it can be divided into alcohol machine (i.e., alcohol fountain offset press, water wheel (i.e., water fountain offset press) and water free offset press.