Abstract: It was found that the oxidation of alizarin red by hydrogen peroxide was catalyzed enzymatically by haemoglobin in an ammoniacal buffer solution of pH 9.8,leading to decoloration of alizarin red.Absorption maximum of the reaction system was found at the wavelength of 525 nm.Linear relationship was kept in the range of 3.0×10-7-8.0×10-5mol·L-1 between values of decrease in absorbance (ΔA) and concentration of hydrogen peroxide.Apparent molar absorptivity (ε525) and detection limit (3s/k) were found to be 1.1×104L· mol-1·cm-1 and 5.2×10-8mol·L-1 respectively.Base on these facts,the method mentioned above was proposed for determination of trace amounts of hydrogen peroxide.Tests for average recovery and precision of the method were peroformed on the base of samples of rainwater and disinfactant liquors,average values of recovery and RSD′s (n=5) obtained were 100.3% and 3.26% respectively.