When operating, the motor drives the bucket wheel slowly rotating through the V-belt and reducer. The sand is put into the washing tank through the feeding chute, and rolls over by the bucket wheel driving. During the rolling, the friction between the sand particles strips the impurities, and breaks the vapor coatings around the particles in order to facilitate dehydration. Meanwhile, massive water is put into the washing tank to form a strong water stream to take the impurities and small percentage of foreign matters away immediately and discharge them from the overflow port. The clean sand is taken by the bucket wheel, and rises up slowly. The water contained in the sand leaks out and falls into the washing tank through the filter screen on each bucket. This process not only finishes the dehydration of sand, but also saves the water. Finally, the cleaned sand is put into the output groove from the buckets, finishing the whole washing process.