Abstract: In order to determine the units' start-up sequence during extended black-start strategy, in this paper,the factors that affect start-up sequence were fully considered from the perspective of whole recovery process firstly, the qualitative factors were quantified by triangular fuzzy numbers and a fuzzy multi-attribute group decision model was established; then the comprehensive weight of expert was calculated by integrating individual authority and the consistency of individual decision information with expert group decision information, the fuzzy multi-attribute group decision making problem for units' start-up was transformed into fuzzy multi-attribute decision problem by integrating all expert decision information; on this basis, the TOPSIS based on triangular fuzzy number was proposed to determine the optimal start-up sequence. The test results on the New England 10-unit 39-bus power system indicated that units' start-up sequence during extended black-start can be optimized effectively by the proposed method, it could provide scientific and reasonable auxiliary information for dispatchers to make decisions.