Abstract: Space is one of the most important concepts of human geography. How human geographers understand space is always changing. Human geography came through three revolutions in 20th century. The connotation of space evolved among the above process. From Kant, Humboldt to Hettner and Hartshorne, the tradition of "areal differentiation" thought that space is an unchanging box within which objects exist and events occur. After WW II, human geography turned gradually from "areal differentiation" to "spatial analysis". New human geographers thought that "spatial relation" is to be defined between objects and events and thereby made relation with the objects and events that constituted a spatial system. Location Theory, which rooted in economics, became the emphases of human geography. New human geographers just took the only physical factor-distance-into account and excluded the other physical and social factors. From the 1970s, a relational or social view of space has been put forward. Henri Lefebvre interpreted how the production in space is changed to the production of space. Although the feminist geographers and cultural geographers were suspicious of the ways whose accounts deriving from historical materialism, they all agreed with the viewpoint of social space or social attribute of space. At the same time, the concept of "space-time" became the focus of spatial epistemology. More recently three basic propositions have emerged from these intertwined formulations. 1) Space and time (or space-time) are now seen as being produced or constituted through action and interaction. 2) Space and time cannot be held fast in fixed compartments, measured intervals or regular geometries. 3) Production of space is inseparable from production of nature. Based on the above, this paper draws a conclusion on the connotation of space. Space is not a given neutral and passive geometry but rather is continuously produced through socio-spatial relations. Space is constituted through social relations and material social practices. In a word, space is the unification of its physical attribute and social attribute.