The invention provides a design method and system for an electricity purchasing combination scheme of an electricity retailing company. Load and electricity price data of an electricity retailing company are collected; an electricity selling influence factor of the electricity retailing company is collected and simulated; an electricity purchasing combination optimization strategy model of the electricity retailing company is constructed and standardized processing is carried out; an electricity purchasing combination optimization strategy model after the standardized processing is obtained by using a parsing method, thereby obtaining an optimal decision vector; de-standardization processing is carried out on the optimal decision vector to obtain an actual decision vector, and profits of the electricity retailing company under the optimal decision are calculated; and according to the actual decision vector and the profits under the optimal decision, an electricity purchasing combination scheme of the electricity retailing company is generated. During the whole process, the load and electricity price data as well as the selling point influence factors of the electricity retailing company are taken into consideration comprehensively; and the n electricity purchasing combination optimization strategy model is built and the profits of the electricity retailing company are calculated; and thus the electricity purchasing combination scheme of the electricity retailing company is generated.