In this paper, the cement water reduction agent from modified lignosulfonate was synthesizd using a new process consisting of pre-oxidation, hydroxymethylation and sulfonation. The optimum synthesis conditions were identified: the oxidizing agent dosage is 15%, reaction temperature is 80-90oC, the dosage of formaldehyde is 30%, reaction temperature is about 95oC, pH is about 9.5. Fluidity of cement paste can be measured under the conditions of the addition of 0.25%, and the water-cement ratio is 0.4%. The results showed the modified lignosulfonate prepared under the above conditions had the better slushing performance. The fluidity of cement paste can reach 178 mm that is close to the high efficiency water reduction agent requirements.