Since the introduction of Avatamsaka Sutra, Huayan School has successfully integrated Indian and the Western culture with the rich culture in China and has achieved the prosperity of Huayan School. The "One Vehicle that contains all Truths" born in this historical background is the core of the Huayan School, with the integration of the "three schools" thoughts and the "five Schools" thoughts. It is often confused with the "Buddhayana". The most significant difference between the two lies in the mana, the former one is more focused on liberation, which is also referred to as "One Buddha Vehicle", and the latter one is more focused on harmony. The concept of Dharmadhatu is another foundation of Avatamsaka. According to the analysis of Monism, it can be divided into the physical Dharmadhatu, or the one-heart Dharmadhatu. The law concept of the physical Dharmadhatu has already been discussed by many researchers, while the research on the usage Dharmadhatu is still lacking. In this paper, I attempt to divide the one-heart Dharmadhatu into four parts: Dharmadhatu for the world, Sukhavati Dharmadhatu, origin Dharmadhatu, and Hsing Chi Dharmadhatu, and explain the meaning of the Dharmadhatu uses "one-heart" and "Dharmadhatu" respectively.
