With the improvement of the living environment and health awareness, there are more and more requirements for packaging materials and printing quality. Small printing defects, result in huge economic losses to printing manufacturer, and further to loose the trust from customers. Because of the lower market price of printed matter, factory has to focus on using raw materials economically. Besides, printing manufacturers also face huge pressures such as decreasing production quantity, increasing product varieties and shortened delivery cycle. Not only to improve work efficiency and reduce costs, but also to satisfy customers' requirements for multicolor, high difficulty and high quality printing. High precision automatic online-inspection system are used to detect defects on printed matter in printing process.