The invention a water level energy power generating device, which comprises a support body and a rotating device, wherein the support body is arranged at water flow position and provided with a generator; the rotating device is arranged in the support body and connected with the generator; the rotating device comprises a plurality of rotating parts; and the rotating parts can link the generator to rotate when shocked by water flow to rotate. The improvement of the device lies in that the rotating device is provided with a plurality of groups of relative sliding rails, and the plurality of therotating parts are moveably arranged on the sliding rails; the rotating device is connected and provided with a control device which comprises a controller and at least one sensor, wherein the controller is connected with the rotating parts of the rotating device; and the sensor is arranged on the support body and used for sensing the capacity of water flow to control the controller so as to control the displacement of the rotating parts on the sliding rails.