In recent years, with the improvement of modern science and technology and the level of information technology, both in the requirements of the printing industry and in the level of people's appreciation, the quality requirements of printed matter are becoming more and more stringent. Printing quality testing has gone through the development process from the initial visual evaluation to the objective evaluation based on a certain theory of density testing and chroma testing, and then to the current online quality testing. Its quality testing methods are constantly updated and developed.