Partitioning the entire electrical network into several sub-regions is a good way to control voltage and reactive power. In this paper, an effective identification strategy is proposed to partition the whole network with typical boundary nodes. Firstly from the point of normal operation, a reactive sensitivity relationship matrix between reactive power sources is formulated to partition the reactive power source. These partitions ensure that there are the right amount of reactive power sources in each sub-region. Secondly, the sensitivity relationship matrix is calculated to figure out the comprehensive sensitivity between the reactive power source partition and load nodes. To solve the problem of the boundary nodes partition ambiguity, this paper presents an identification strategy based on perturbation increasing the load power. Through the analysis and calculation for IEEE39 node system, the simulation results achieve the apparent division to the boundary nodes. The partitions avoid the ambiguity effectively. The simulation results with IEEE39 node system demonstrate the effectiveness of this partition method.