The analysis and modeling of road network capacity provides a useful measure for urban planning and traffic management. Therefore, the primary purpose of this research is to construct a novel approach of modeling the capacity of road network, based on the theory of space and time consumption. Based on the analysis of model parameters, a bi-level model is proposed to determine and optimize the capacity of road network Meanwhile, this paper elaborates on solution algorithm for its upper and lower level model. Taking the area of Ming Dynasty City Wall in Xi’an, China into account as a case study, the effectiveness of this proposed model is verified. The results presents that the model’s validity is verified. The results show that the main road network capacity in city wall of Ming Dynasty is 721883 pcu/d.