The invention discloses a method of determining content of methanol, isobutanol, and isoamylol of alcohol, and relates to methods of determining alcohols. The method of determining the content of the methanol, the isobutanol and the isoamyol of the alcohol comprises steps as below sequentially: (1) alcohol sample pretreatment processing steps: moving sample alcohol into a volumetric flask, adding interior label solution into the volumetric flask, using absolute ethanol to dilute the solution to a constant volume measured by scales, blending the solution to be used as the solution to be tested; (2) blank experiment: adding no samples, and repeating the step (1); (3) carrying out combination analysis of gas chromatography-mass spectra analysis of the samples and the blank sample. The method of determining the content of the methanol, the isobutanol, and the isomylol of the alcohol achieves accurate precise quantification analysis of the content of the methanol, the normal propyl alcohol, the isobutanol and the isoamylol of the alcohol through method improvement and replacing of detectors. The method of determining the content of the methanol, the isobutanol and the isoamylol of the alcohol is simple to operate and fast and accurate.