A method of detection hydroxyl radical (·OH) produced by electrochemical oxidation in organic wastewater treatment was developed. Benzoic acid with weak fluorescence may reacted with hydroxyl radical to produce 3-hydroxybenzonic acid with intense fluorescence, whose characteristic fluorescence excitation and e-mission wavelength were at 305 nm and 410 nm. The 3-hydroxybenzonic acid was separated from electrochemi-cal oxidation system by HPLC. Two major hydroxylated products were quantified corresponding to 3-hydroxyben-zonic, 4-hydroxybenzonic acid. Therefore the quantity of hydroxyl radical in the reactive system should be pri-marily calculated. The optimal experimental program was obtained by studying the determination conditions, which were benzoic acid of 1.0 mmol/L, electrolysis time of 60 min, current density of 39 mA/cm2, supporting electrolyte (Na2SO4) of 0.02 mol/L, and the low rate of sparged-air of 25 mL/s. The results show that this method is stable, simple and rapid and can be used as a convenient method for the determination of hydroxyl radical.