Abstract: With the emergence and application of the soft normally open point（SNOP）, the operation mode of supply area interconnection of multiple voltage levels and multiple balance nodes will become the normal state in the modern distribution network, which make the operation of integrated ring and multiple rings in distribution network and online optimization scheduling operation possible. Therefore, new requirements are put forward for the power flow calculation method of large-scale distribution network with multiple supply areas and multi-feeder interconnection. In view of this, this paper dismantles multiple rings shaped by SNOP in a large-scale multi-balance bus distribution network in actual engineering project, according to the radiated area of each balance bus. Therefore, the network can be divided into several blocks. The breadth-first search algorithm performs hierarchical layering of buses, and adopts an improved back/forward sweep method. For the PV operation mode of SNOP, the reactive power initial value of the PV bus is estimated by the reactive power sharing method, and then the power addition method is used to obtain the variation of the reactive power. The reactive power addition method converts a PV bus into a PQ bus that can be processed by the back/forward sweep method. Finally, the power flow calculation results of the actual 396-bus distribution network in a certain place show that the adopted method is effective and fast.