The invention discloses a method used for measuring content of furfural in transformer oil via high performance liquid chromatography. The method comprises following steps: 1, pretreatment of transformer oil, wherein oxidation of the transformer oil with an oxidizing agent is carried out, after oxidation, ethanol is taken as an extraction agent for extraction so as to obtain an extracted solution 1, and ethanol is also taken as an extraction agent to extract the untreated transformer oil so as to obtain an extracted solution 2; and 2, yield measurement of oxidation of the transformer oil into furfural, wherein the oxidation method and the oxidation conditions in the step 1 are adopted, and the reaction yield of oxidation of furfural in the transformer oil into furoic acid is carried out; 3, high performance liquid chromatography measurement, wherein a phenylpropyl bonded silica gel chromatographic column is adopted, a sodium citrate aqueous solution and methanol are taken as the mobile phase, wherein the pH value of the sodium citrate aqueous solution is controlled to be 4 to 5; and 4, measurement of furfural content. The method can be used for measuring furfural in transformer oil accurately.