Abstract: According to transit flow characteristics in special event and city size,urban transit route set to study is defined.Based on the defined stop service radius,stop service areas are obtaind by geometric partitioning and they in every traffic zone are known by overlapping.Considered that passenger traffic flow is in direct proportion with service areas,transit assignment model is built.Regarding the relations between stops and lines,and transfer flow and background volume,a passenger flow model is built.Finally,transit assignment in Wukesong Gymnasium is taken for example.Transit flow is assigned and compared with the true transit flow.The minimum error is 3% which can satisfy transit operation demand.