In this paper, the heat transfer performance of nanofluids is predicted by numerical analysis methods. The nanoparticles used in this study is SiO2, with concentrations of 1, 2, 3vol.%, and the base fluid is water. Reynolds number of nanofluids ranges from 10,000 to 50,000. A numerical study on the heat transfer characteristics of nanofluid was conducted using a single-phase model. The temperature of the fluid entering from the inlet of the tube is 293.15K. A constant heat flux of 31,650W/m2 was applied at the wall, and the thickness of the wall was ignored. Heat transfer coefficients, thermal conductivity and Nusselt number were selected as indicators for comparing heat transfer performance of nanofluids. As the nanofluid concentration increases, the temperature and velocity distribution by the cross section of the coil tube and straight tube increased. As the Reynolds number increases, temperature difference between inner direction and outer direction reduced in coil tube. For straight tube, the temperature difference between the wall and the center of the tube also decreased.