Road construction area expands rapidly in China which challenges the conservations of natural resources. While available studies largely focused on consumptions at project level, this study integrated material flow analysis and life cycle assessment methods to quantify the material stocks and environmental impacts of urban road system. Remote sensing images were processed to extract road network skeletons. Taking Nanjing as an example, the results show that: 1) arterial road stores the largest amount of materials (42.9 million tons) of entire road system; 2) macadam occupies nearly 80% of total material stocks; 3) increase of road class coincides with the increase of material stock per unit area and enhances the material utilization efficiency; 4) arterial road is over-emphasized and expressway is still of a small scale in Nanjing. The methodology developed in this study provides a useful tool for road planning to effectively control resource depletion in the long term.