It is true that some paintings are printed, some are dug out and some are old. When high imitation calligraphy and painting is made by screen printing or watermarking, the works with simple pen and ink will be imitated, while the works with too complicated pen and ink cannot be imitated because of its multi-level and high harmony. Therefore, when encountering suspicious screen printing or watermark, we must pay more attention to identification. There are many ways to identify, and the most important thing is to learn and understand pen and ink. When Mr. Yang Shilang emphasized the importance of pen and ink and fakes, he smiled and said, "It seems that I can't bully the world with three points, so I don't need to steal my name to learn from me with seven points." . When the old trafficker visited Mr. Xu Bangda with his teacher, he repeatedly emphasized the importance of judging from the level of pen and ink skills when talking about calligraphy and painting appraisal. Mr Qian Ji also saw this. For example, Chinese painting emphasizes that "ink is divided into five colors", which is one of the bases: is the ink color changing rich? Is it harmonious and dry? Especially when the level is too far-fetched and discordant, it is necessary to doubt whether it is screen printing or watermarking. In recent years, the auction price of calligraphy and simple Chinese paintings has been declining, which is caused by too many screen prints and watermarks and people's lack of pen and ink knowledge.