1. The main body of the dewatering machine is a filtering device formed by stacking a fixed ring and a moving ring with a screw shaft penetrating through it. The front section is the concentration section, and the rear section is the dehydration section. 2. The filter gap formed between the fixed ring and the moving ring and the pitch of the screw shaft gradually decrease from the concentration part to the dehydration part. 3. While the rotation of the screw shaft pushes the sludge from the thickening section to the dewatering section, it also continuously drives the traveling ring to clean the filter gap to prevent clogging. 4. After the sludge is concentrated by gravity in the thickening section, it is transported to the dewatering section. As the filter gap and pitch gradually become smaller during the advancement process, and under the blocking action of the back pressure plate, a great internal pressure and volume are generated. Keep shrinking to achieve the goal of full dehydration.