The invention discloses a sag water recycling system and method of a wet slag removal system. The sag water recycling system involves a slag slurry tank, a descaling reactor, a first heat exchanger, aboiler make-up water source and a boiler make-up water system; an outlet of the slag slurry tank communicates with an inlet of the descaling reactor, an outlet of the descaling reactor communicates with a heat release side inlet of the first heat exchanger, a heat release side outlet of the first heat exchanger communicates with the slag slurry tank, an outlet of the boiler make-up water source communicates with a heat absorption side inlet of the first heat exchanger, and a heat absorption side outlet of the first heat exchanger communicates with the boiler make-up water system. The sag water recycling system and method can avoid the influence of the slag water scaling on the heat exchanger, and meanwhile, recovery of the slag water heat quantity is realized.