It was found that micro amounts of oxalate showed a very strong catalytic effect on the slow reaction between K 2Cr 2O 7 and Orange Ⅳ in a diluted sulfuric acid medium in a water bath at 70 ℃ . Orange Ⅳ exhibited a sensitive second order derivative polarographic wave at -0 50 V( vs . SCE). This provides the basis for a sensitive and selective catalytic kinetic method for oxalate determination with second order derivative oscillopolarography. The effects of sulphuric acid, K 2Cr 2O 7, and orange Ⅳ concentrations, reaction temperature and reaction time were investigated. A calibration curve of oxalate in the range of 0 1-2 0 μg/mL was obtained by the fixed time procedure. The detection limit was 0 03 μg/ mL. The possible interference from co existing substances or ions was examined. The new method has a high sensitivity and a good selectivity compared to other existing methods for oxalic acid determination. It has been applied to the determination of micro amounts of oxalate in real urine samples with satisfactory results. It was found that micro amounts of oxalate showed a very strong catalytic effect on the slow reaction between K 2 Cr 2O 7 and Orange IV in a diluted sulfuric acid medium in a water bath at 70 ° C. Orange Ⅳ exhibited a sensitive second order derivative polarographic wave at -0 50 V (vs. SCE). This provides the basis for a sensitive and selective catalytic kinetic method for oxalate determination with second order derivative oscillopolarography. The effects of sulphuric acid, K 2 Cr 2 O 7, and orange IV concentrations, reaction temperature A calibration curve of oxalate in the range 0 1-2 0 μg / mL was obtained by the fixed time procedure. The detection limit was 0 03 μg / mL. The possible interference from co existing substances or ions was examined. The new method has a high sensitivity and a good property compared to other existing methods for oxalic acid determination. It has been applied to the determination of micro am ounts of oxalate in real urine samples with satisfactory results.