When machine working, the motor start through V-belt, reducer and gear after reducing the speed then taking the impeller rotation slowly. The sand enter into the washing channel from the feeding end and rolling under the working of the impeller, in the meantime doing the mutual grinding. Eliminate the impurity covering the surface of the sand, and destroy the water steam layer wrapping of the sand in favor of water taking off. Meanwhile putting into the water, it can form enhanced water flow and take away the impurity and foreign matters in small proportion, finally the sand fall into the discharging channel through the rotation of the impeller and concluded in sand washing.