Abstract: In order to accurately describe the operation states of urban transport systems,the relationships between various elements of urban transport systems are analyzed.The reasons leading to traffic congestion and the impact of con-gestion pricing are thoroughly described.Considering the interactions between economy,population and environment in conjunction with the impact of the policy of car purchasing restriction,a system dynamics model is developed and used to study the effects of congestion pricing.Effects of the congestion pricing are investigated in the following two aspects:traf-fic and environment impact with a focus on traffic performance index,average speed,and NO x emissions.The predicted results of traffic conditions and environment impact in Beijing between 201 5~2020 show that it would have the best effect when the congestion pricing is 1 6 Yuan per vehicle with a main target of alleviating traffic congestion;higher than 1 6 Yuan per vehicle will result in the waste of road resources.Otherwise,if taking both traffic and environment impact into consideration,when congestion pricing is set to 1 1 Yuan per vehicle,which is slightly lower than the average value of travel time,it cannot only alleviate traffic congestion,but also reduce emissions.