The invention relates to a reproducible polytertiaryamine sulfur dioxide absorbent and a preparation method thereof. The absorbent comprises the following components: (1) polytertiaryamine having a mass concentration in the range from 1% to 80%, which is taken as the major component of the absorbent, wherein the polytertiaryamine exists in a solution in the form of unionized polytertiaryamine, partially ionized quaternary ammonium salt and completely ionized quaternary ammonium salt due to addition of an acid difficult to volatilize; (2) a phenol or quinone material having a mass concentration in the range from 0.01% to 1%, which is used as an antioxidant of the absorbent; (3) 1-50wt% of acid difficult to volatilize, which is used as the cosolvent and stabilizer for the polytertiaryamine; (4) 0.1-10wt% of monoalcohol amine, which is used as an activator of the absorbent; (5) 10-90wt% of water. The absorbent absorbs sulfur dioxide in mixed gases at a low temperature and releases the absorbed sulfur dioxide gas at a high temperature to generate a sulfur dioxide by-product having a dry basis concentration greater than 99%; the absorbent can be recovered and reused.