Abstract: Based on the catalytic oxidation of p-dihydroxybenzene at pre-anodized platinum electrode,and on the principle of bi-amperometric detection of irreversible electrode reaction,a method of direct FI-biamperometric determination of p-dihydroxybenzene was proposed.In the bi-amperometric detection system,when a potential of 0.3 V was applied,irreversible catalytic oxidation of p-dihydroxybenzene was carried out at one of the Pt-electrode,and irreversible reduction of platinum oxide carried out at the other Pt-electrode.The proposed method was proved to be of high sensitivity and selectivity and was suitable to be used in automatic on-line analysis when cooperated with the flow-injection technique.The electrode reaction was performed in a B-R buffer of pH 1.89.Linear relationship between the oxidation peak currents and concentrations of p-dihydroxybenzen was obtained in the range of 8.0×10-6-6.0×10-4mol·L-1,with the detection limit (3S/N) of 4.0×10-7mol·L-1.Test for precision was performed at 1.0×10-5mol·L-1 p-dihydroxybenzen,the value of RSD (n=10) found was 2.8%.Using simulated water sample as matrix,recovery test was made by standard addition method,the values of recovery were found in the range of 98.6%-103.9%.