Abstract: Urban transportation system have always been represented by network models and been researched basing on these models．The paper proceeded from network macro topological features of urban public transportation and divided urban public transportation system into two difierent models，the trafic-1ine network and traffic-station network．It analyzed urban public transportation system by introducing some basic and important topological parameters which were used in network analysis；calculated and analyzed these two network topological parameters．The public transportation system in Beijing is an example．Finally，from the angle of transportation engineering and city planning，some impo rtant perspectives and proposals were disclosed to the public transportation．

Key words: urban transit system, network analysis, topological parameters, transportation engineering

摘要： 城市公共交通系统通常是用网络来表示并在此基础上对其进行研究的。从研究城市公交系统的网络宏观拓扑性质出发，将城市公共交通系统划分为公交站点网络和公交线路网络，通过引入网络分析中一些常见的重要拓扑参数来对城市公共交通系统进行分析，以北京市公交系统为例，计算并分析了这两种网络的拓扑参数，并从交通工程的角度对这些拓扑参数的具体意义进行了研究，最后从交通工程和城市规划的角度为城市公交系统的建设提出了一些建议。

关键词: 公共交通系统, 网络分析, 拓扑参数, 交通工程