We proposed a new type of freestanding Catalase (EC 18.104.22.168) (Cat) modified paper electrode based on Fe3O4 crystals decorated freestanding reduced graphene oxide (rGO) paper (Cat-Fe3O4/rGO) using a facile electro-deposition method. This enzyme modified paper electrode was used for the specific determination of hydrogen peroxide (H2O2). Structural, chemical, and morphological characterization of the Fe3O4 crystals formed on rGO paper was investigated by (i) using scanning electron microscopy (SEM), (ii) energy-dispersive X-ray spectroscopy (EDS), (iii) X-ray photoelectron spectroscopy (XPS), (iv) X-ray diffraction spectroscopy (XRD), (v) Raman spectroscopy, (vi) electrochemical impedance spectroscopy (EIS) and (vii) cyclic voltammetry (CV) techniques. The Cat enzyme was successfully adsorbed on the Fe3O4 nanocrystals surface which was demonstrated by fluorescence microscopy. The Cat-Fe3O4/rGO paper electrode showed excellent electrocatalytic activity toward H2O2. It is found that Cat-Fe3O4/rGO paper electrode shows a wide linear range, high sensitivity, and a low detection limit for H2O2 detection.