Influence factors on urban public transport distributing rate of Beijing as a case study

China economy rapidly developed in recent years. Beijing is the representative large city with preferable construction of urban public transport system in China. Therefore, it has important practical significance to research the influential action of urban public traffic modes in Beijing public transport system. On the basis of the four factors- safety factor, convenience factor, comfort factor and cost factor, as well as the traffic distributing rate of various transport modes, it is analyzed the interaction of the urban public traffic modes and also demonstrated the competition and coupling relation of the three urban public traffic modes-rail transit, bus and taxi. At the present stage, it's raised some suggestion on development direction based on the reaserch of the method system dynamics in this paper.