Abstract: Objective: To alleviate government financial pressure, TOT (tolloperatetransfer) method is creatively adopted to carry out PPP (publicprivate partnership) model for Tianjin Metro Line 2 and Line 3 existing projects. It is valuable to summarize the specific process and methods of implementation in this project for the reference of other ones. Method: The implementation process of TOT method in Tianjin Metro Line 2 and Line 3 PPP projects is summarized in detail. The difficulties encountered in the implementation process are summarized through analysis of Tianjin Metro PPP project asset ownership hierarchy, and targeted solutions are proposed accordingly. Result & Conclusion: The implementation of PPP models through TOT method in urban rail transit existing projects involves five stages: identification, preparation, procurement, implementation and handover of the project. Careful handling is required for issues such as employee transfer and placement, division and transfer of shared interface management. In 2021, Tianjin Metro Line 2 and Line 3 PPP projects, as the first rail transit existing asset PPP program in China, successfully completed the bid handover, directly activating funds exceeding 15 billion RMB.