The invention provides a peak-clipping and valley-filling optimizing method of a load curve, and relates to a method for optimizing a peak-clipping and valley-filling effect. The method comprises the following steps of establishing a peak-clipping and valley-filling optimizing model; and solving the peak-clipping and valley-filling optimizing model, so as to obtain the optimum peak load and peak-valley difference. The method has the advantages that the defects of subjectivity and only one solution by one-time optimizing in the traditional peak-clipping and valley-filling optimizing method are overcome; a plurality of groups of peak loads and peak-valley differences can be solved, so a user can objectively select the optimum peak load and peak-valley difference according to actual requirements; and compared with the traditional algorithm, the better optimizing effect can be ensured, the heavy pressure generated by peak adjusting and frequency adjusting is avoided, and the power qualities, such as voltage and frequency, are improved.