The increasingly complex structure of urban rail transit network and the increasing demands of passenger flow bring great challenges to the operation and management of urban rail transit. As the basis of rail transit operation management, passenger flow is an important prerequisite for the adjustment of train operation and the reasonable clearing of ticket. Therefore, from the perspective of individual passengers, this paper analyzes the passengers' travel process in the “black box” of the rail transit network, proposes the concept of “travel chain”, and disassembles the passenger's travel process into specific arc segments for analysis. This paper will focus on the analysis of the impact of passenger retention phenomenon caused by the full load of the train on the actual travel time of passengers, as well as the analysis and calculation method of passenger retention rate at the station. Finally, a case analysis was conducted based on the actual network conditions of the Shenzhen Metro and passenger flow data.