On the basis of the principle of molecular design, polycarboxylate superplasticizer was prepared by means of free radical polymerization with MPEGAA, AA and MAD as major monomers. The effects of total monomer concentration, initiator and reaction time on polymerization rate of the polycarboxylate superplasticizer were investigated, and the polymerization kinetic relation was obtained as r∝C0.5903Ic0.8089Me-5465/T. The reducing performance of the superplasticizer was determined by means of measuring the fluidity of the cement paste, and the optimum reaction conditions were obtained, e.g.:the molar ratio of n(MPEGAA)∶n(AA)∶n(MAD) is 1∶1.50∶0.36, the amount of initiator is 2.5wt% of monomer, the reaction temperature is 60℃, and the reaction time is 6h.