The human-water relationship is one of the most important relationships between human and nature. The human-water relationship discipline is a new interdisciplinary subject that studies the human-water relationship. Developing basic equations and models is one of the core contents of in-depth research on human-water relationship. Based on previous research and interdisciplinary findings, this study proposes the “four processes” in the human-water system(the water cycle process, the material cycle process, the biological process, and the humanistic process). The basic equations, the coupling and calculation method of the “four processes” are summarized and presented. The framework for constructing a distributed human-water relationship model considering the “four processes” and the construction idea of human-water relationship simulator are proposed. An application case study in the Qinhe River Basin is also provided. The “four processes” in the human-water system are important foundations for characterizing the human-water relationship. The basic equations of the “four processes” are the fundamental equations for studying the human-water relationship discipline. The model constructed by coupling basic equations is an important tool for simulating human-water relationship issues. This study lays the foundation for further improving the human-water relationship discipline and provides ideas for in-depth research on the human-water relationship model.