An experimental study of heat transfer characteristics of narrow rectangular channels with rib turbulators for Re in the range of 10000-60000 was performed. To simulate the actual geometry and heat transfer structure of blade/vane internal cooling passage, each of the test channels was welded by four stainless steel plates. Because of the three dimensional heat conduction in the walls and heat conduction between the ribbed and smooth walls, the measured temperature distribution along the axial direction of the test channel is a smooth continuous curve, and when the Re is low, the average Nu of the ribbed and smooth walls are nearly the same. For each aspect ratio channels, the average Nu for the channel of α=45° is about 15 to 25 percent higher than that of α=60°. In addition, we have developed the semi-empirical correlations, covering the range of Re, to predict heat transfer coefficient of the channels. The correlations can be used in the design of turbine blade/vane cooling channels.