Most of Taiwan rivers are rapid and steep with large capacity of vertical erosion. The hydraulic structures crossing the river such as drop structures, check dams and weirs have been widely used to decrease the flood erosion, stabilize riverbed, protect structures crossing the river, and provide civil water and irrigation. The hydraulic structures make upstream channel stable while the sediments cannot be transported downstream and stay in front of riverbed of drop structures on the other way. These structures usually induce the change of upstream slope and super critical flow condition which makes a large impact force on the downstream with the result of destroying energy dissipation structures. This paper aims at studying the theoretical formula of impact force, impact location and impact angle with the variation of upstream and downstream channel slopes. Then, the slope effect ratio δ and slope influence value η are used to study their effects on the above three hydraulic parameters.