The invention discloses an SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) detection method of true protein of a dairy product and an identification atlas database of the method. The SDS-PAGE detection method comprises the steps: after pretreating a sample to be detected, detecting by using discontinuous polyacrylamide gel electrophoresis, shooting by using a UVP gel imager and analyzing by combining with Labwork software, associating the protein spot density of a lane with the concentration of true protein in a sample, and performing contrast with a standard curve so as to calculate a protein content. According to the SDS-PAGE detection method of the true protein of the dairy product, provided by the invention, the constitution and content of the true protein in the dairy product can be rapidly, sensitively and conveniently detected, and the sample obtained by treatment in the process can be directly applied to measurement of the content of the total protein in the dairy product. The purpose of obtaining a target result by one-time measurement is actually realized. Meanwhile, by adopting the method, an SDS-PAGE identification atlas database of the true protein of the dairy product is established. The SDS-PAGE detection method can be used for comparing SDS-PAGE of the dairy product to be detected so as to be directly judged and evaluated, and has a very good application prospect.