The three dimensional flow field of an open channel flow with a moderate adverse pressure gradient was measured by a Hot-film anemometer. It is found that the intensity of the secondary flow which normalized by a mean bulk velocity increases in the flow direction. The secondary flow affects on mean velocity profiles and friction velocity distributions. In particularly, as the intensity of the Reynolds stress increases in the flow direction, the production of turbulence energy is increased. Therefore, the intensity of the turbulence energy increases.