Road is a comprehensive system composed of people, road, vehicle, etc. Vehicle driving is greatly affected by road geometric parameters. Firstly, the influences of straight line, circular curve, slope length, slope and other parameters on vehicle driving are analyzed. Then the vehicle model, road model and comprehensive simulation model of man-vehicle-road are established by using Carsim software, and the reliability of the model is analyzed by using double line shifting method. Finally, based on an urban expressway, the variation law of vehicle driving characteristics is analyzed by using speed variation coefficient Kv and sideslip safety coefficient Ks. The research results can provide certain theoretical guidance for the geometric design of the similar urban roads.