Abstract: Suzhou rail transit has entered the new stage of network-based operation. With the change of line network scale and passenger flow demand, it is essential to further refine the transfer connection scheme of last trains. Based on the current operation status and passenger flow characteristics of Suzhou rail transit line network, the optimization method of line network last train connection scheme is designed. The last train timetable of each station is calculated by Spanning Tree Algorithm. Considering the restrictions of minimum reserved time of line construction and number of train depots in line network on the departure time of the last train at the departure station, and the demand of railway hub night-time passenger flow, the last train connection scheme is rectified, and the optimized last train connection scheme of Suzhou Rail Transit Lines 1-4 is obtained. Research results show that, compared to the existing last train scheme, the connection of the optimization scheme is more reasonable and more suitable for passenger and operation requirements.