Based on user equilibrium theory,a study was made of the interaction between the traffic flow of cars and buses in super-network,the traffic flows of the two transportation modes were optimized to maximize the bus-sharing ratio.Then,based on the assumption that the total travel cost in urban transportation network consisting of the travel cost of cars and the buses,two-tier location model was established to optimize the total travel cost and land cost.Finally,a case study was made of the two-tier location model and then gives some useful suggestions on optimization location of transportation terminal.