According to the development process of underground space, this paper summarizes the new thinking from underground space 1.0 to underground space 5.0. The basic characteristics were discussed explicitly during the development of the underground evolution. The key technologies and typical cases from underground space 1.0 to underground space 5.0, then the characteristics and mechanism of the underground space development were revealed in the end. The research shows that the overall form of underground space is from "one underground point" to "one underground line", and then weaves "one underground network". The scale is becoming larger and larger. It is built into "an underground city" through the advanced concepts of aboveground and underground three-dimensional planning and regional overall development. With the development of artificial intelligence, digital twins Cutting edge technologies from green low-carbon to carbon neutralization are gradually widely used, and will eventually be transformed and upgraded into "smart three-dimensional city" and "green underground space" in the foreseeable future.