Water-soluble sulfonated acetone–formaldehyde (SAF) resins were synthesized by the reaction among acetone, formaldehyde, and sodium bisulfite. The surface activity of SAF resins and their performance in concrete were evaluated. The effect of molecular weight (MW) of synthesized SAF resins on the performance of the superplasticized concrete was determined. The results showed that the SAF resin has the potential to be developed as a superplasticizer used in concrete.