The reliable operation of power transmission and transformation equipment affects the safety and stability of the power grid. The aging diagnosis of oil-paper insulation equipment is one of the key technologies for on-line monitoring and diagnosis of power transmission and transformation equipment. As an important feature for evaluating the aging state of oil-paper insulation equipment, furfural needs to be accurately detected. Raman spectroscopy based on Raman effect can quickly and accurately detect the dissolved aging characteristics in oil. It is therefore important to increase the sensitivity of the Raman detection of dissolved furfural in oil. In this paper, deionized water was used as extractant to extract and Raman spectroscopy of furfural in oil. Under the same experimental conditions, methanol was used as extractant to find the characteristic Raman peak of the furfural molecule of 1371 cm-1. The Raman spectra were compared on a certain concentration gradient, and the minimum test sample concentrations were 1.38 mg/L and 2.75 mg/L, respectively, and the repeatability test was performed. The comparison results show that the Raman spectroscopy of furfural molecules in oil based on deionized water as extractant has lower detection limit and repeatability than methanol as extractant, which has contributed to the rapid and non-destructive test of furfural content in oil.