Nanofluid as advanced coolant able to enhance capability heat transfer of cooling system, but with abnormal enhancement of viscosity of nanofluids have raised doubt on its thermal performance in practical application. In present paper, a thermal performance analysis has been conducted on various types of metal oxide water based nanofluids. The evaluated metal oxide water based nanofluids were Al2O3, CuO, MgO, TiO2, SiO, ZnO, and ZrO2 water based nanofluids. A performance factor is defined under fully developed laminar pipe flow with heat transfer to evaluate the thermal performance of nanolfuids. A systematic data reduction method to organize the experimental data of thermal conductivity and viscosity of various nanofluids is presented in this paper. Based on the comparison of enhancement of thermal conductivity and viscosity, thermal performance of various types of nanofluids is evaluated and their ranking is presented.