The Prussian blue nanoparticles(PBNPs) were prepared by a self-assembly process, on a glassy carbon(GC) electrode modified with a poly(o-phenylenediamine)(Po PD) film. The stepwise fabrication process of PBNPs-modified Po PD/GCE was characterized by scanning electron microscopy(SEM) and electrochemical impedance spectroscopy. The prepared PBNPs showed an average size of 70 nm and a homogeneous distribution on the surface of modified electrodes. The PBNPs/Po PD/GCE showed adequate mechanical, electrochemical stability and good sensitivity in comparison with other PB based H_2O_2 sensors. The present modified electrode exhibited a linear response for H_2O_2 reduction over the concentration range of 1–58.22 mmol L ~(-1)with a detection limit of ca. 0.8 mmol L ~(-1)(S/N = 3), and sensitivity of 3187.89 m A(mol L ~(-1)) ~(-1)cm 2using the amperometric method. This sensor was employed for the H_2O_2 determination in real sample and also exhibited good interference resistance and selectivity. The stepwise fabrication process of PBNPs-modified Po PD / PBNPs was prepared by a self-assembly process on a glassy carbon (GC) electrode modified with a poly (o-phenylenediamine) The PBNPs were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy. The PBNPs showed an average size of 70 nm and a homogeneous distribution on the surface of modified electrodes. The PBNPs / Po PD / GCE showed adequate mechanical, electrochemical stability and good sensitivity in comparison with other PB based H_2O_2 sensors. The present modified electrode exhibited a linear response for H_2O_2 reduction over the concentration range of 1-58.22 mmol L -1 with a detection limit of ca. 0.8 mmol L ~ (- This sensor was employed for the determination of H 2 O 2 in real sample and also exhibited the same sensitivity as 3187.89 m A (mol L -1) -1 (cm -1) using the amperometric method good interference resistance and selectivit y