Fluid flow and heat transfer of helium in a minichannel has been experimentally studied to investigate the effect of high pressure and high temperature flow conditions. The experimental apparatus consists mainly of gas booster, pre-heater, electric furnace, and cooler. The test section tube is a round minichannel of 1.397 mm inside diameter, made of Inconel 600. The ranges of the major experimental parameters in this study are 2000 ～ 34000 of Reynolds number, 20～110 kW/m2 of wall heat flux. The experimental results showed that the heat transfer coefficient were not affected by inlet temperature, inlet pressure, and heat flux. Pressure drop was not also affected by inlet temperature, inlet pressure, and heat flux.