Based on the electrochemical principle of quinone, this paper determined the peak current of 1, 4-naphthoquinone reduction on free fatty acids. Polypyrrole （Ppy）film was prepared by incorporation of tetrabutylammonium perchlorate （TBAP）as doping anion, during the electropolymerization of pyrrole onto a platinum（Pt） electrode in acetonitrile solution by using cyclic voltammetric（CV） method. Linear voltammetry （LV） was utilized for the measurement of oleic acid and linoleic acid by modified electrode.The analytical curve was linear in the oleic acid and linoleic acid concentration from 5.3×10-3mol/L to 7.9×10-2mol/L and 9.6 ×10-6mol/L to 1.28×10-3 mol/L with a limit of detection of 1.6×10-3mol/L and 3.0×10-6mol/L （ S/N = 3 ） respectively. The correlation coefficient（ R2 ） was 0.9948 and 0.9922 respectively.The modified electrode was used for determination of vegetable oil acid value in some real samples such as olive oil,corn oil, peanut oil, soybean oil and sesame oil.The results showed that the chemical modified electrode method was a simple and rapid acid value determination method to replace the alkaline titrimetric method.%基于醌的电化学还原原理，利用1，4-萘醌对游离脂肪酸的还原峰电流的测定，检测植物油中油酸和亚油酸的浓度，从而求出所测植物油的酸价。采用循环伏安法在乙腈溶液中聚合吡咯单体于铂电极表面制备化学修饰电极Ppy／ClO。一／Pt，用线性伏安法检测油酸和亚油酸浓度。结果表明：在浓度分别为5．3×10-3 -7．9×10-2mol／L和9．6×10-6-1．28×10-3mol／L之间，还原峰电流与油酸和亚油酸浓度呈现良好的线性关系，相关系数（R2）分别是0．9948和0．9922，亚油酸和油酸的检出限为3．0×10-6mol／L和1．6×10-3mol／L（S／N=3）。并且将该化学修饰电极用于植物油橄榄油、玉米油、花生油、大豆油和芝麻油中酸价的检测，结果表明，化学修饰电极法是一种简便、快速实用的酸价滴定方法，可以作为碱滴定法的替代方法。
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