Supercritical water reactor is one of the generation IV reactors which is basically a creative mixture of conventional PWRs and supercritical pressure steam boilers. Application of nanoparticles provides an effective way of improving heat transfer characteristics of conventional coolants; thus, utilization of a nanofluid coolant in the conceptual design of this reactors is quite reasonable and inevitable. Reactor coolant at supercritical pressure dose not experience any phase change and is heated up to 500 degrees C in three pass core design. In this paper, thermal hydraulic analysis of applying a water base Al2O3 nanofluid with different nanoparticle mass fractions were investigated using a porous media approach. Calculations showed that, utilization of nanofluid can enhance the core outlet temperature and increases the heat transfer coefficient in Super-heater zones.