The electric motor runs slowly with the impellor after decelerated by the belt, decelerator and gears wheel. The sand and stone flow into washing launder from feeding launder, rolls with the impellor, and grinds each other. The impurity covering the sand is washed away. At the same time, adding more water, the strong water flow will take waste and some low-weight wastes away from the washing launder. Through the above process, the washing function is finished. The clean sand and stone are lift up by vane. When it goes up slowly, the water begins to drop through the mesh and fall back in the washing launder. On one hand, water is removed from the sand and stone; on the other hand, the water can be fully used. Finally, the sand and stone goes to the out launder from the rotary impellor to finish the washing task.