Abstract: Step-pool system is a typical bed micro-morphology in high gradient (>3%) mountain rivers, which creates extremely high turbulence intensity and thus dissipates most of the flow energy. An artificial step-pool system was constructed in the Wenxia River downstream of the Wenxia Reservoir and experiments were conducted to study the characteristics of turbulence in step-pool system. The velocity and turbulence intensity were measured with the three dimensional acoustic doppler velocimeter (Vectrino) made by the Nortek Cooperation. The sampling frequency of the instrument was 200 Hz. The fluctuating velocity was measured at 3 cross sections at upstream of the step, on the step, in the pool and along the thalweg. The flow discharge was controlled stable during the measurement at 10 L／s, 50 L／s, 100 L／s, 150 L／s, 290 L／s and 420 L／s. The results showed that the flow around the step-pool was very three dimensional. At the cross-sections upstream of and on the step, turbulence intensity was small and the mean velocity was high. In the pool, however, the mean velocity was greatly reduced and turbulence intensity became extremely high. The relative turbulence intensity, defined as the ratio of the turbulence intensity over the mean velocity, was around 0.1 at upstream of the step, and increased to 8.0 in the pool. Most of the flow energy transformed from mechanical energy to the tubulence energy as water flowed from upstream of the step to the pool. The Reynolds stress was calculated with the fluctuating velocity components and the results showed that the Reynolds stress in the pool was about 50 times higher than that on the step. Following increasing flow discharge from 10 L／s to 420 L／s the energy dissipation ratio reduced from 91% to 64%.