By applying the segmentation and composition principles of ecosystem,the structure and interface of earth ecosystem are fully elaborated,and corresponding model diagrams are established to display its composition and interconversion. The research finds that earth ecosystem includes three sub-ecosystems: terrestrial ecosystem,marine ecosystem and atmospheric ecosystem. The impact sequence of sub-ecosystems on earth ecosystem is atmospheric ecosystem > marine ecosystem > terrestrial ecosystem. Based on the segmentation and composition principles of ecosystem and the application of earth ecosystem structure and interface,we give new explanations to Taoism and Taiji with the eight diagrams,which contributes to theoretical research of natural science.