The invention discloses a stain remover for sewage treatment, prepared by uniformly mixing white lime and furnace ash in a ratio of 1: 1 to 3. A sewage treatment method comprises the following steps: adding the stain remover in a water pool; then, pouring sewage into the water pool and stirring so that the stain remover and the sewage are uniformly mixed; stopping stirring and precipitating for 15 minutes so that the stain remover and suspended matter in the sewage are together precipitated at the bottom of the water pool; and discharging clear water above sediment after precipitation so as to be repeatedly circulated and recycled and using remnant stain remover and sediment in the water pool as the stain remover to continue using in the next sewage treatment so as to avoid adding a new stain remover in the water pool. The stain remover added once can continuously repeatedly treat the sewage for 5 to 7 times according to the water quality pollution conditions of the treated sewage. The invention has little investment, fast effect, simple equipment maintenance, small floor area, economy and practicability.