Abstract:With the continuous improvement of the pace and level of urban development and construction in China, many cities have planned CBD as the engine of urban social and economic development. The following problems such as high development intensity, strong traffic demand and traffic congestion in the morning and evening have also been highlighted. Therefore, many cities have planned underground ring roads to make up for the deficiency of ground road network. Through the research on the characteristics of CBD road network and combined with the road network capacity theory, this paper puts forward the calculation model of whether to build underground Ring Road, so as to provide theoretical support and technical means for quantitative analysis for the planning and construction of underground ring road.