The invention relates to a method and system for determining a bidding strategy at a power demand side. The method includes: determining the cost price of adjustment power segments corresponding to respective load data subclasses according to the cost curve of the demand-side load adjustment power, and determining the declared price corresponding to the load data subclasses according to the cost price and a profit proportion; according to the number of historical bidding success rate of a current demand-side load using the declared price corresponding to the load data subclass to which the current demand-side load belongs as a quotation plan, determining the bid winning probability function of the quotation plan; and according to the optimized bid winning probability function, determiningan optimal profit ratio. The bidding strategy determined by the technical solution of the present invention has a higher probability of winning the bid, and can adapt to the needs of the new environment, and further increase the competitiveness of the demand-side resource.