Method of inclined-tube settling water is installed above the mud suspended layer dip angle of 60 degrees inclined-tube formation, and suspended solids in raw water, solids or by adding coagulant alum flocs formed after, at the end of tube surface area to accumulate into a thin layer, relying on gravity slide back into mud suspended layer, and then sank into the mud set. Sludge discharge pipe into tank further processing or utilization. Supernatant pipes rose to set out gradually, can be discharged or reused.