The invention discloses a method for combined power supply based on an industry mean peak-valley difference rate. The method comprises the following steps that the typical industries and the typical day of an area with combined power supply to be carried out are selected; representative users are extracted from the selected typical industries, and statistics is carried out on the peak-valley difference rate of the representative users in the typical day; statistics is carried out on the peak-valley difference rate section of each typical industry to obtain the industry mean peak-valley difference rate; load classification is carried out on the selected typical industries; the industries with the large peak-valley difference and the industries with the small peak-valley difference or the industries with complementary peaks and valleys are classified into the same transformer or transformer substation, and combined power supply is carried out. The influence of load characteristics on a power distribution network and electric energy quality is fully considered, and the problems that at present, the uneven loads of the transformer are ubiquitous, and the capacity-load ratio of the transformer substation is too low can be effectively solved.