This article examines the concept of tianren heyi, the “unity between human and nature”, and its role in the theory and practice of Chinese mountain and water painting. The author first traces its philosophical roots in the Yijing and the Yi Zhuan theory of the three talents (heaven, earth and human), and in Zhuangzi, Laozi and the Huangdi neijing, which describe a holistic, non-anthropocentric order in which human beings and nature share the same structure and the same vital flow of qi. From the post-Han period, this relationship became central to pictorial theory: Zong Bing introduced the Dao into landscape painting, prefiguring Xie He’s qiyun shengdong, while Zhang Zao’s maxim “outwardly learn from nature, inwardly attain the source of the heart” and Dong Qichang’s call to “read ten thousand books and walk ten thousand li” joined study with direct experience of nature. Rooted in eremitic culture, this attitude informs Guo Xi’s landscapes in which one can “travel” and “dwell”, Huang Gongwang’s sketching from nature and Shitao’s identification with mountains and rivers. The author concludes that, unlike Western perspective, which places the viewer outside nature, shanshui painting offers a positive, conciliatory environmental critique that encourages love and protection of nature.