An investigation of heat transfer rate of a heat plate under a slot jet was studied numerically. For enhancing the heat transfer rate of the heat plate, a block moves back and forth on the heat plate. Then the thermal boundary layer on the heat plate is destroyed by the moving block and a new thermal boundary layer reforms immediately as the block passes through. Consequently, the remarkable heat transfer enhancement of the heat plate is attained. This subject belongs to a kind of moving boundary problems, the modified arbitrary Lagrangian Eulerian (ALE) method is suitable for solving this subject. The results show that the maximum increment of heat transfer rate is about 200% in the largest velocity case.