Hemoglobin?(HB) is a protein in red blood cells which contains iron. It is used to transport oxygen around the human body. Hemoglobin?is found in the red blood cells of almost all vertebrates. Hemoglobin has peroxidase activity. In the presence of hydrogen peroxide, hemoglobin can catalyze the substrates 3,3 ', 5,5' - tetramethylbenzidine (TMB) to produce a blue compound which has a maximum absorption at 595 nm. Thus, the activity of native rabbit hemoglobin was measured by its ability to catalyze the substrates of TMB. The reaction was performed in PBS, pH 7.4 ( Assay Buffer), ainitiated by addition 40 μL of various concentrations of HB (diluted by Assay Buffer) to 160 μL of TMB. Incubated at 37 ℃ for 20min, then read at a wavelength of 595 nm immediately. The result was shown in figure 1, and the OD value was in a linear relationship with the concentration of HB.