Horseradish peroxidase (HRP) and toluidine blue (TB) were incorporated in polyion complex membrane composed of double stranded DNA(dsDNA) and chitosan prepared on the surface of an glassy carbon (GC) disk electrode to fabricate highly sensitive and selective reagentless H2O2 biosensor. The embedded-TB in the DNA/chitosan membrane exhibited excellent electrochemical redox property with an electron transfer rate constant of 3.12 ± 0.5 sec−1, and shuttled electron effectively from the base GC electrode to catalytic center of the HRP. Under the applied potential of -0.22V (versus Ag/AgCl) and pH 7.0, the resulting electrode (HRP/DNA–TB/chitosan/GCE) exhibited rapid (<10 s) and sensitive response to H2O2. The calibration curve of H2O2, plotting steady-state cathodic current versus H2O2 concentration, was linear up to 0.1mM with a detection limit of 1 μM H2O2 (S/N = 3). The H2O2 response was scarcely interfered by ascorbic acid and uric acid, which potentially reduce oxidized intermediate of the HRP and interfere with the response of peroxidase-based electrodes.