The invention relates to a method for measuring drug contents, particularly to a method for measuring danshensu, m-methyl-danshensu, protocatechualdehyde, and protocatechuic acid in the human blood plasma. The method comprises the following steps: 1) preparation of reference substance storing solutions: weighting reference substances of danshensu, m-methyl-danshensu, protocatechualdehyde, and protocatechuic acid, and dissolving the reference substances with methanol to obtain reference substance storing solutions of danshensu, m-methyl-danshensu, protocatechualdehyde, and protocatechuic acid; 2) preparation of an internal standard solution: dissolving an internal standard substance of vanillic acid with methanol to obtain the internal standard solution; 3) a treatment method of a blood plasma sample: taking the blood plasma sample, adding the internal standard solution, methanol, hydrochloric acid, and ethyl acetate into the blood plasma sample, performing uniform mixing, performing centrifugation of the obtained mixture to obtain a supernatant ethyl acetate layer, drying the ethyl acetate layer, re-dissolving the ethyl acetate layer with methanol, and performing centrifugation of the obtained solution to obtain supernatant liquid of the blood plasma sample; and 4) content measurement: by adopting LC-MS/MS chromatography, injecting the reference substance storing solutions and the supernatant liquid of the blood plasma sample into a chromatographic instrument to obtain a chromatogram, and calculating concentrations of danshensu, m-methyl-danshensu, protocatechualdehyde, and protocatechuic acid in the human blood plasma according to the areas of chromatographic peaks in the chromatogram.