Abstract: Objective: The integration of the multiple levels of rail transit has become a crucial trend in the current and future development of China rail transit system. By improving the combined usage efficiency of different rail transit systems and establishing an integrated service level, support can be provided for the integrated development of multilevel rail transit (abbreviated as IDMRT). This IDMRT can cast a positive impact on the flow of factors within regions and stimulate new economic growth points, contributing substantially to the improvement of regional economic integration. Therefore, it is necessary to conduct research on IDMRT.Method: The impact of IDMRT on regional economic integration is analyzed by focusing on alleviating regional transportation pressure, optimizing the allocation of regional factors, and promoting regional urbanrural circulation. The processes and approaches of IDMRT in Tokyo and Paris are introduced, and characteristics of which in metropolitan areas are summarized through case studies. Objectives and principles for IDMRT are proposed, along with development approaches in terms of functionality integration, network integration, and operation integration.Result & Conclusion: The goal of IDMRT is to enhance its competitiveness in aspects including time, service, and efficiency. The principles for IDMRT involve organically integrating various rail transit systems, reflecting comprehensiveness, coordination, convenience, policy support, and rationality. The development approaches include functionality integration, implementing train coline operation; network integration, establishing a hierarchical hub system; and operation integration, establishing an integrated operation system.