The space art of human settlements involves architecture and fine arts, thus space environment and space art are the key to understanding urban space art while space is the source of the concept or meta-notion. This paper, by defining the concept of space and interpreting spatial structure under different context, stresses the virtual imaginary space intentionally, i.e. the space of image or artistic conception, which has been neglected by the previous space concepts, thus trying to establish basic structure of the particular space art of mountain human settlements.