The novel magnetic composites of ordered mesoporous carbon/Fe304 were prepared with a micro-wetness impregnation method. The composites were characterized by transmission electron microscope and X-ray diffraction. Hemoglobin was immobilized onto the surface of the composites, and was shown to keep its biological activity well. The electrochemical behavior of Hb was studied, and a pair of well-defined, quasi-reversible cyclic voltammetric redox peaks was obtained, which was characteristics of Hb Fe（III）/Fe（II） redox couples. The formal potential （E01）, the electron transfer number （n）, and transfer coefficient （a） were calculated to be 0.306 V, 1.226 and 0.51, respectively. The average apparent heterogeneous electron transfer rate constant （Ks） obtained for Hb was 0.0144 s-1. Linear sweep voltammet- ric measurement of Hb indicated that the peak currents of Hb were linear to its concentration ranging from 3.00 × 10-6 to 1.50 × 10-4 mol/L with the detection limits of 0.270 ×10-6 mol/L.