Abstract: Objective For passenger route choices between urban rail transit station pairs in existing models, the passenger flow distribution is often based on uniform assumptions. But in reality, the number of effective routes between two stations and the proportion of passengers choosing each route vary significantly, and influencing factors are complex. Therefore, it is necessary to analyze and identify the influencing factors and law behind differences in passenger route choices. Method Based on mobile signaling data, the actual travel routes of China Unicom users as Shanghai urban rail transit passengers are obtained, along with the number of passengers choosing each route. The stability of round-trip routes between rail transit station pairs and the differences in passengers route choice proportions are observed. The causes of the differences in typical round-trip route choice proportions and their impact on passenger travel choices are analyzed from the perspectives of route travel time, interchange conditions, and ride comfort. Result ＆ Conclusion Differences in round-trip route choices between urban rail transit station pairs are mainly influenced by factors such as the passengers’ familiarity with rail transit network, the route travel time, the relative position of interchange stations, the number of interchanges, the interchange time and walking distance during interchanges, and the available seats in train compartments. The research findings provide a reference for optimizing urban rail transit passenger route choice models.