Abstract: Digital twin city has played an important role in ensuring the smooth progress of urban modernization.This paper takes the third round construction planning of Ningbo rail transit as an example,and demonstrates that the static and multi temporal digital twin city can meet the application needs of urban planning and construction.It systematically expounds the construction method of the unified big scene of the digital twin city.Digital twin city integrates multi-source and multi-scale data, such as 2D data, landform, real 3D model, rail transit information model, underground pipeline model, etc.Use digital twin city for two-dimensional and three-dimensional line selection of rail transit.Connect the design, construction, operation and maintenance after the connection planning and line selection.Rail transit life cycle management forms a perfect closed loop in digital twin city.In the future, digital twin city will accelerate their expansion to other fields and has broad prospects.

Key words: digital twin city, rail transit, life cycle management, teleconference, planning and route selection