AbstractModification of sodium lignosulfonate (SLS) via combined oxidation-sulfomethylation was employed to prepare concrete superplasticizer. It was found that the oxidation of SLS by peroxyacetic acid facilitated the subsequent sulfomethylation. After modification, both the molecular weight and sulfo group content were significantly increased, and thus the performance of SLS as water reducer was improved. With the water to cement ratio at 0.4 and 0.3% (w/w) modified SLS, the fluidity of cement paste could reach 185 mm, which was 15% higher than that with unmodified SLS. It was also comparable to the performance of commercial naphthalene superplasticizer under the same conditions.