Abstract: Geographic space is the basic characteristic of geographical information and the core concept of geographical information science. The being of geographical space is the fundamental of geographical information science. This paper presents an idea about geographical information science, that is, geographical information science is about the study of the human-machine-earth interaction system with a focus on the conception of geographic space.The ontology of geographical space is elaborated in the context of the human-machine-earth interaction system towards a complete understanding of geographical space.