The invention discloses a method for detecting an A2-beta-casein content in a dairy product. The method comprises the following steps: preparing a sample and a standard substance, if the sample is milk powder, adding water to prepare an emulsion, and performing centrifugation and degreasing on the emulsion or cow's milk; adding a buffer, performing vortex blending, performing standing for 10-120 min, and performing centrifugation for 5-20 min; taking a lower clear liquid, adding the buffer for metering a volume, performing vortex blending, and using a PTFE filter membrane with a thickness of 0.45 [mu]m for filtering for computer detection; performing a HPLC detection analysis, and employing a gradient elution program for elution, wherein a mobile phase A is 0.1% of trifluoroacetic acid anda mobile phase B is 0.1% of acetonitrile. The detection analysis method can realize detection and analysis research on A1-beta-casein and A2-beta-casein subtype states in common milk, through cooperation adjustment of pretreatment and chromatogram conditions, full separation of two subtypes is realized, whether a cow's milk raw material belongs to the pure product A2-beta-casein subtype cow's milk can be rapidly determined by combining with the standard substance, the current gene detection analysis methods can be substituted, detection analysis research difficulty can be simplified, and thedetection analysis cost is reduced.