A controlled splitting strategy for the power system based on the multi-level graph partitioning method is proposed.By referring to the graph theory and the characteristics of power system comprehensively，the optimal splitting solution can be found in three phases of coarsening，initial partitioning and refinement.In the coarsening phase，a novel power flow tracing method，which starts from the synchronous generators in parallel rather than from the individual generator，is given to improve the efficiency of coarsening.After initial partitioning is completed by the greedy growing graph partitioning algorithm，the preliminary splitting boundary will be refined by a proposed0-1programming method with the topology connected constraints taken into account to ensure high splitting quality and connectivity of sub-graphs.Finally，IEEE118-bus and300-bus test systems are used to validate the effectiveness of the splitting strategy.