Common thermal EOR methods face diverse challenges such as low efficiency in thin reservoirs, high energy loss and environmental issues. Recently it has been found that Electromagnetic Heating method can solve most of these problems. While EM-Heating has many advantages like low startup time, outstanding decrease in oil viscosity, and negligible environmental effects, it encounters serious restrictions such as low penetration and high energy consumption. Overcoming these limitations will improve effectiveness of EM-Heating. Several research groups have reported that nanoparticles enhance the thermal characteristics of the fluids. The objective of this work is to use nanoparticles in order to change thermal properties of water and therefore improve the thermal EOR methods efficiencies. In this work nano fluids were prepared by MgO, Al2O3, Fe3O4 and SiO2 nanoparticles. These samples were heated using electromagnetic waves and trends of their temperature were recorded. Finally their thermal properties were compared to reference case which was de-ionized water. Also the effect of nanoparticles concentration was studied. Nanoparticles were found to have a remarkable effect on microwave absorption and thermal conductivity of water. The type, concentration, stability, and size distribution of nanoparticles in the fluid had the most influences on thermal properties enhancement. Al2O3 nanofluid found to have superior features. Also an optimum interval was defined for concentration of this nanoparticle. The result and observations are expected to be useful in further studies and efficiency improvement of EM-Heating and the other thermal EOR methods.