The invention discloses a liquid chromatography-based SBS modified asphalt dosage test method, and belongs to the technical field of material detection. The method comprises the following steps: carrying out liquid chromatographic scanning on an SBS modified asphalt sample solution with different dosages, carrying out baseline correction on obtained chromatograms by using an SBS modified asphalt liquid chromatogram optimum baseline area integration technology, and detecting the SBS modifier chromatographic peak area of every standard sample; and establishing a relationship between the SBS modifier chromatographic peak area and the SBS dosage to form an SBS modifier dosage standard curve. The method is used for controlling the dosage of SBS modified asphalt with an unknown dosage in labs, indoor production and onsite use places. The method solves the problem of unable segmentation of continuous chromatographic peaks through chromatographic software, has high precision in detection of the SBS modified asphalt dosage, and is a simple and effective treatment method.