In order to achieve higher thermal efficiency and power output, the gas turbine inlet temperature of gas turbine engine is continuously increased. However, the increasing temperature may exceed the melting point of the blade material. Rib turbulators are often used in the midsection of internal cooling ducts to augment the heat transfer from blade wall to the coolant. This study uses computational fluid dynamics (CFD) to investigate side-wall heat transfer of a rectangular passage with the leading/trailing walls being roughened by continuous or truncated ribs. The inlet Reynolds number is ranging from 12,000 to 60,000. The detailed three dimensional (3D) fluid flow and heat transfer over the side-wall are presented. The overall performances of ribbed passages are compared. It is suggested that the usage of truncated ribs is a suitable way to augment the side-wall heat transfer and improve the flow structure near the leading edge especially under the critical limitation of pressure drop.