Power system state estimation has been one of the heart function of monitoring and control in power grid EMS/DMS. The correct methods of SE not only improve the accuracy and calculation efficiency of state estimation, but also enhance the numerical stability of estimation results. Firstly, the current grid partition criterions are introduced. And the core research problems of various partition methods are analyzed. Moreover, the advantages and disadvantages of power system partition state estimation based on network topology and geographical location, AMI and MAS are reviewed. After that, the state estimation based on the fast decoupling and the phase sequence decoupling are the current effective solution for handling the state estimation of three-phase balance and three-phase unbalanced power system from the point of view of increasing the calculation speed of regional transmission and distribution network. Finally, the existing research problems on the partition and decoupling of state estimation are summarized, then some suggestions for further research are proposed. This work is supported by Science and Technology Foundation of Guizhou Province (No. [2012]2157) and Innovation Foundation for Graduates of Guizhou University (No. 2017064).