As China's urbanization accelerates, single-mode rail transit systems are no longer sufficient to satisfy increasingly diverse commuting needs. There is a growing demand for an integrated, multi-level rail transit model tailored to China's specific context—one that supports metropolitan and regional development through better network coordination. The study reviews the current state of rail transit integration in China across four aspects: (1) integration scenarios, (2) infrastructure and rolling stock, (3) transport operations and management, (4) legal and policy support. Key challenges include low ridership on certain routes, fragmented ticketing systems, high operational costs, uncoordinated planning of suburban lines, and difficulties in building a stable passenger base. These issues call for new operational models and improved technical standards. In response, the study outlines a development strategy that includes clear goals, pilot examples, and key tasks. It recommends a "cross-city + radial + multi-branch" network layout, unification of technical standards, smart service platforms, and stronger coordination mechanisms. By aligning planning, technology, operations, and policy, the goal is to achieve seamless integration of multi-modal rail systems and support more balanced regional growth.