Disclosed is a drop water power generating device. Specifically, one or more river reaches with a high slope fall are selected from a drainage basin of a river or reservoir diversion canal or a hydropower station tailrace, and miniature dams are arranged at the initial sloping positions of the river reaches to block water so as to form a front pool. According to a scheme 1 adopted in the downstream river reach, water is channeled to climb a viaduct through an inverted-siphoning-type pressure water pipe to be connected with a suspension down pipe, drop water is formed in the pipe to drop and emit energy so as to drive a water turbine to rotate, then, a power generator is driven to run and generate power, and therefore the drop water power generating device is formed. According to a scheme 2, one end of an over-bridge-type open channel or a cylindrical water pipe penetrates though the miniature dams to be communicated with the front pool, the other end of the over-bridge-type open channel or the cylindrical water pipe decreases gradually above the river reach drainage basin and extends to the viaduct corresponding to a hydropower station water head to be fastened and located and further be connected with the suspension down pipe, water flows form drop water in the pipe to drop and emit energy so as to drive the water turbine to rotate, the power generator is then driven to run and generate power, and the drop water power generating device is formed.