The direct electrochemistry of hemoglobin (Hb) immobilized on a hexagonal mesoporous silica (HMS)-modified glassy carbon electrode was described. The interaction between Hb and the HMS was investigated using UV-Vis spectroscopy, FT-IR, and electrochemical methods. The direct electron transfer of the immobilized Hb exhibited two couples of redox peaks with the formal potentials of ?0.037 and ?0.232V in 0.1M (pH 7.0) PBS, respectively, which corresponded to its two immobilized states. The electrode reactions showed a surface-controlled process with a single proton transfer at the scan rate range from 20 to 200mV/s. The immobilized Hb retained its biological activity well and displayed an excellent response to the reduction of both hydrogen peroxide (H2O2) and nitrate (NO2-). Its apparent Michaelis-Menten constants for H2O2 and NO2-were 12.3 and 49.3μM, respectively, showing a good affinity. Based on the immobilization of Hb on the HMS and its direct electrochemistry, two novel biosensors for H2O2 and NO2-were presented. Under optimal conditions, the sensors could be used for the determination of H2O2 ranging from 0.4 to 6.0μM and NO2-ranging from 0.2 to 3.8μM. The detection limits were 1.86×10-9M and 6.11×10-7M at 3σ, respectively. HMS provided a good matrix for protein immobilization and biosensor preparation.