The electric motor runs slowly with the impeller after decelerated by the belt, decelerator and gears wheel. The sand and stone flow into washing launder from feeding launder, rolling with the impeller, and grinding with each other. The impurity covering (on) the sand is washing away. Adding more water at the same time, the strong water flow will take away waste and some low-weight wastes from washing launder. The above is the whole washing process. The clean sand and stone is lift up by vane. When it goes up slowly, the water begins to drop through the mesh and fall back into 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 impeller to finish the washing task.