Abstract: When a power system suffers from some big disturbance, its security and stability will be threatened. To completely track the electro-mechanical transient process after disturbance, a new power system state estimation (SE-PS) based on dynamic state estimation of synchronous generator (DSE-SG) is proposed, and how to further apply the results of DSE-SG to system-side SE-PS is studied to achieve the unified estimation of the dynamic and static state variables of the entire system. Firstly, focusing on the solution of electro-mechanical transient DSE of the whole power system, the infeasibility of complete synchronization, the realization conditions of decoupling estimation, and the necessity and significance of re-coupling estimation are discussed. Secondly, based on the concepts and mathematical models of DSE-SG and SE-PS, the status, roles, relationships, and data flows of the variables and equations involved are clarified, which lays a theoretical foundation for the selection of re-coupling media and the determination of interface mode and forms the realization framework and idea of re-coupling estimation. Furthermore, two different interface modes are proposed, and their specific implementation methods and processes are given in detail. Finally, the proposed method is implemented in an IEEE9-bus system. The simulation results show that the method can track the electro-mechanical transient process of the whole power system well and realize the unified estimation of dynamic and static state variables. Compared with the traditional SE-PS without DSE-SG, the proposed method has higher accuracy and a more remarkable filtering effect.