In the present study, natural convective heat transfer of Fe 3 O 4 /Ethylene glycol nanofluid around horizontal platinum wire in electric field was investigated through the computational fluid dynamics method (CFD) using COMSOL 4.3 a. The free convection heat transfer coefficient changes with volume concentration and various electric field intensities were studied. The effect of the number and shape of electrodes on heat transfer was studied as well. Then the results were compared with the experimental data. Numerical results Show that in absence of electric field, free convection heat transfer coefficient increases with volume concentration of nanoparticle and enhancement of natural convection heat transfer coefficient in low Rayleigh numbers is greater than high Rayleigh numbers. Moreover, electrohydrodynamic with low energy consumption Increases free convection heat transfer coefficient. In presence of electric field, enhancement of natural convection heat transfer coefficient in low Rayleigh numbers is greater than high Rayleigh numbers, because in high Rayleigh numbers the effect of the secondary flow is reduced against flow caused by buoyancy force. Free convection heat transfer coefficient of ethylene glycol in the presence of electric field in V=12.5 kV and low Rayleigh numbers, increases 40%. Free convection heat transfer coefficient of nanofluid in the presence of electric field is greater than heat transfer coefficient also. Results show that with replacing the plate electrode instead of needle electrodes, free convection heat transfer coefficient increases more. Furthermore, free convection heat transfer coefficient with three needle electrodes is greater than one needle electrode. Keywords : free convective heat transfer, nanofluid, electrohydrodynamic, modeling, computational fluid dynamics