Abstract: Folic acid was determined by linear sweeping voltammetry in a B-R buffer solution of pH 6.8,using the amino-silicon oil modified carbon paste electrode as working electrode.A sensitive oxidation peak of folic acid was obserbed in the voltammogram at the peak potential (Epa) of +0.84 V (vs.SCE).Linear relationship between values of peak current and concentration of folic acid was kept in the range of 1.6×10-7-6.5×10-6mol·L-1,with value of detection limit (3S/N) 7.2×10-8mol·L-1.The time of accumulation taken for folic acid was 100 s.As shown by the results of cyclic voltammetric study of electrochemical behavior of folic acid,the redox electrode reaction at the aminosilicon oil modified carbon paste electrode was proved to be an irreversible adsorption process.