Dilute dispersion of silver nano-particles in pure water was employed as the working fluid for conventional 1mm wick-thickness sintered circular heat pipe. The nanofluid used in present study is an aqueous solution of 10 and 35nm diameter silver nano-particles.The experiment was performed to measure the temperature distribution and compare the heat pipe temperature difference using nanofluid and DI-water. The tested nano-particle concentrations ranged from 1, 10 and 100mg/l. The condenser section of the heat pipe was attached to a heat sink that was cooled by water supplied from a constant temperature bath maintained at 40°C.At a same charge volume, the measured nanofluids filled heat pipe temperature distribution demonstrated that the temperature difference decreased 0.56–0.65°C compared to DI-water at an input power of 30–50W. In addition, the nanofluid as working medium in heat pipe can up to 70W and is higher than pure water about 20W.