Qichang Dong's article " Zen-Painting Studio Essays " is not only a collection of his perception of Buddhism through his Zen Joy and friendship, but also the root of his art thoughts on painting and calligraphy. Understanding the objects and contents of Zen friendship is of great significance for Qichang Dong to develop and form his artistic view —"plain"— in the late Ming Dynasty. This article disclosed Dong Qichang's daily practice and experience of Buddhism by the following: 1. The external communication: to detect the Buddhist understanding of others; 2. The internal observation: to enlighten the self experience from the ancient and "plain". Based on this idea, this paper first discusses the differences between the contents of Rongtai Collected Works and Zen-Painting Studio Essays, and derives that the phenomena such as addition, deletion, merging, word change, and inversion of the contents are common in the late Ming Dynasty. Moreover, understanding Qichang Dong's Zen friendship is helpful to appreciate the origin and development of his artistic thought, which is fundamental for the aesthetic connotation of calligraphy, which will be discussed at the end. It is hoped that through the course of this study, the formation and influence of Qichang Dong's calligraphy art thought can be understood, and the supplementary effect of Buddhism on the interpretation of calligraphy art idea can be confirmed.