The invention discloses a buoyancy water pumping device for water conservancy and hydropower. The buoyancy water pumping device structurally comprises supporting legs, a water storage tank, a supporting transverse plate, connecting bolts, a protective cover, an LED illuminating lamp strip, a fixing rod, a water guiding barrel, an overhauling door, a flow guiding pipe, a water pumping control hostand a water pumping pipeline. According to the device, an arranged floating ball can move up and down according to the rising height of the water level of the sea level, the floating ball touches a contact to start an energy supply device in the process of moving up and down, the energy supply device reduces the high consumption and has an energy-saving and environment-friendly effects at the sametime by means of water conservancy power generation, the energy supply device drives a main driving device after being started to drive a contact driving mechanism inside a main machine room to starta suction pump to realize the water pumping work and open a water pumping channel by driving a baffle connecting mechanism inside the main machine room, when the equipment is closed, the channel is closed, so that equipment failures caused by horizontal plane deep water backflow are avoided.