The invention discloses a provincial power grid online dynamic partitioning method, and relates to a power grid partitioning method. At present, provincial dispatching operators lack provincial powergrid partition operation monitoring and analyzing functions, and no practical tools and means are used for monitoring real-time partition information and equipment operation states of a power grid. The provincial power grid online dynamic partitioning method comprises the steps of: model updating, network topology, dynamic layered partitioning and partitioning models. The dynamic layered partitioning is based on a topological model, the topological model is divided into an ultrahigh voltage main network, a high voltage main network and a high voltage distribution network according to voltage grades to generate a two-layer graph model of the high voltage main network and the high voltage distribution network. According to the technical scheme, dynamic partitioning of the provincial power grid is achieved on line, the output partitioning model data provides intuitive and clear power grid partitioning operation information for dispatching operators, the perception and active control capacity of primary equipment of the current power grid is improved, a model data basis can be provided for functions such as power supply reliability analysis and transfer capacity monitoring and analysisof partitioning loads, and safe and stable operation of the power grid is guaranteed.