The invention provides a partitioning scheme optimizing method and device for power system restoration after blackout, and relates to the technical field of power systems. The method comprises the following steps: establishing a first optimizing model on the basis of the target strategy of fewest connecting lines between subsystems in a power grid and pre-established electrical characteristic constraint conditions of the power grid; solving the first optimizing model based on a preset solver to obtain a first partitioning scheme; processing the first optimizing model based on cutting constraint conditions to obtain a second optimizing model; solving the second optimizing model based on the solver to obtain a second partitioning scheme; evaluating the first partitioning scheme and the second partitioning scheme respectively according to established evaluation indexes to obtain evaluation results of the first partitioning scheme and the second partitioning scheme so as to determine a main partitioning scheme and a standby partitioning scheme from the partitioning schemes on the basis of the evaluation results. Therefore, restoration time after power grid faults can be shortened effectively, and high reliability of power grid restoration after the faults is guaranteed.