Selecting a reasonable black-start mode is helpful to decide the optimal black-start scheme. This paper analyses the cooperation of black-start strategies, black-start modes and black-start schemes, and then studies the constraint conditions and characteristics of black-start modes. Based on analyzing the selection principle of the black-start mode comprehensive assessment index system, it extracts the system and handles it with hierarchical processing. In the hierarchical assessment index system, principal component analysis is used to remove the correlation between the indexes in the index layer, and entropy value method is used to obtain the ultimate evaluation value in the criterion layer. At last, it analyses the sensitivity of the method. A practical example proves its effectiveness and feasibility. This method is able to provide a reference for the schedulers to choose the optimal mode.