Abstract: Based on its peroxidase property,a new method of catalytic spectrophotometric determination of hemoglobin (Hb) was proposed.In an ammoniacal buffer medium of pH 9.5,oxidation of acid chrome blue K (ACBK) by hydrogen peroxide was catalyzed by hemoglobin,leading to acceleration of color-fading of the reaction system.Under the optimized reaction condition,the magnitude of decrease in absorbance (ΔA) due to catalytic effect was found to keep a linear relationship with the concentration of Hb in the range of 7.0×10-10-9.0×10-8mol·L-1,with its detection limit (3Sb/k) of 1.7×10-11mol·L-1,and apparent molar absorptivity of 3.9×108L·mol-1·cm-1.In application of the proposed method to the determination of Hb in urine,values of RSD′s (n=5) obtained were in the range of 1.9%-4.2%,and values of recovery were in the range of 96.0%-102.0%.A brief discussion on the mechanism of the enzyme catalysis was also given.