In this article, high-sulfonated melamine-formaldehyde (HSMF) resins were prepared with a sulfite/melamine (S/M1.5) molar ratio. During the sulfonation process, the reaction temperature and the added velocity of sodium bisulfite affecting the properties of the resin were studied. In the condensation stage, where the pH range is 6.0 and the temperature is about 25 degreesC, the condensation time was prolonged above 24 h. The stability and water solubility of the resin was improved greatly. It is an effective superplasticizer at small dosages of admixture.