The construction of modular digital smart grid, as a result, the complexity of the power grid is increasing and new technologies and schemes are emerging, more sophisticated design means are needed. Therefore, the author puts forward the research on the intelligent design of three-dimensional digital substation. The emergence of 3D design has changed the status quo of difficult collaboration among multiple disciplines under the traditional design mode, and improved the level of substation design from the perspective of life-cycle management. Firstly, the characteristics of digital collaborative design are analyzed, the construction of 3D model library of equipment is explained, and the intelligent auxiliary control system of substation is described, taking a project as an example, after checking the electrification distance, it can be found that the electrification distance between the camera arranged in the 220kV power distribution unit area and the lightning arrester of the outgoing line does not meet the requirements, and the number of equipment is 3, the application of three-dimensional design is described from the aspects of video monitoring system, automatic fire extinguishing system, etc, its application in the front end equipment layout, model retrieval, collision inspection between safety distance and foundation, buried pipe design, material statistics and other dimensions of these systems were shown in detail, the method of 3D design is deeply studied and applied to the practical engineering design of high voltage substation. The space characteristics of 3D design can be used to realize complex underground pipeline layout, cable optimal layout, collision inspection, construction simulation, visual display, etc.