Hydrogen peroxide biosensor based on the silica cavity array modified indium-doped tin oxide (ITO) electrode was constructed. An array of silica microcavities was fabricated by electrodeposition using the assembled polystyrene particles as template. Due to the resistance gradient of the silica cavity structure, the silica cavity exhibits a confinement effect on the electrochemical reactions, making the electrode function as an array of “soft” microelectrodes. The covalently immobilized microperoxidase-11(MP-11) inside these SiO2 cavities can keep its physiological activities, the electron transfer between the MP-11 and electrode was investigated through electrochemical method. The cyclic voltammetric curve shows a quasi-reversible electrochemical redox behavior with a pair of well-defined redox peaks, the cathodic and anodic peaks are located at −0.26 and −0.15 V. Furthermore, the modified electrode exhibits high electrocatalytic activity toward the reduction of hydrogen peroxide and also shows good analytical performance for the amperometric detection of H2O2 with a linear range from 2×10−6 to 6×10−4 M. The good reproducibility and long-term stability of this novel electrode not only offer an opportunity for the detection of H2O2 in low concentration, but also provide a platform to construct various biosensors based on many other enzymes.Highlights► Hydrogen peroxide biosensor based on silica cavity array electrode was constructed. ► The electron transfer of MP-11 was investigated through electrochemical method. ► The linear range for Hydrogen peroxide determination was from 2×10−6 to 6×10−4 M. ► The detection limit was 4×10−7 M.