As the change of the traffic environment, the design of level intersections on some urban roads can no longer meet the current traffic situation, which cannot withstand the current traffic flow load, making the operation efficiency of the intersections low. Based on the optimization theory and the design guidelines of intersections on urban roads, the optimal signal period was screened, the optimal optimization scheme was matched, and the road traffic capacity model of intersections was established in this paper, through the optimal quantitative analysis on the traffic capacity, saturation and service level of intersections. Taking the intersection of Jingcheng Road and Fangyuan Road in Chengdu as an example, the traffic flow characteristics of the intersection were analyzed by video observation method and field investigation method, and the model was verified with VISSIM software. The research results show that compared with the original intersection, the optimized intersection can separate the traffic flow in time and space, to improve the operation efficiency. The research results can be used as a reference for the optimal design of level intersections.