The invention relates to a pretreatment method for a blood plasma sample for detecting endogenous amino acids and belongs to the technical field of medical testing. The method comprises the core steps: specifically adsorbing a nonpolar biological matrix from blood plasma by adopting a solid adsorbent, and then, carrying out selective elution on amino acid ingredients in the blood plasma by adopting an eluent, so as to obtain an endogenous amino acid ingredient. Specific operation flows are as follows: the blood plasma sample is diluted by a certain proportion of acidifying aqueous solution, then, the sample is added into the specific solid adsorbent, and the selective elution on the endogenous amino acids in the blood plasma is achieved through optimizing parameters such as use level and proportioning ratio of an eluting solvent. The obtained endogenous amino acid ingredient is concentrated and then is redissolved, and the synchronous detection on the endogenous amino acids in one step is achieved under specific chromatography and mass-spectrometry conditions. The pretreatment method has the characteristics that the operation is simple, convenient and controllable, the ratio of recovery of target objects is high, the reproducibility is good, and the like; the interference to the quantitative detection on the amino acids caused by nonpolar substances in the blood plasma is avoided, and the sensitivity and accuracy of detection are improved.