The invention discloses a main power distribution integrated power failure range assessment method considering regional interconnection transfer. A power failure range assessment system is formed based on a power failure range assessment module. The method comprises the following steps: firstly, partitioning the power system according to the existing power system network topology connection relationship, and simultaneously forming a network relationship matrix and a load transferable region; when a certain area has a fault or is overhauled, the capacity-to-load ratio of the load transferable area is defined, reasonable transferable of the fault load is achieved according to the magnitude, and the fault power failure range is evaluated. On the basis, in the load distribution process, the constraint conditions of the interconnection lines are considered, the optimized transfer strategy based on the one-time load transfer method is achieved, and the fault power failure range is further narrowed. Simulation and system analysis show that the use efficiency of equipment can be effectively improved, reasonable load transfer and consumption of a fault area are achieved, and therefore powerfailure loss caused by faults or overhaul is reduced.