The　preparation　and　performance　of　a　modified　polymelamine　sulphonate　based　superplasticizer　(M-PMS)are　introduced　in　this　paper.　The　results　show　that　the　M-PMS　has　better　dispersion　ability　and　strength　enhancing　properties　in　comparison　with　traditional　melamine　superplasticizer　and　naphthalene-based　superplasticizer.　Meanwhile,　the　M-PMS　shows　satisfactory　adaptability　with　cellulose　viscosity　enhancing　admixture.　The　M-PMS　could　obviously　improve　concrete　strength　under　negative　temperature　environment,　and　thus　suitable　for　concrete　construction　in　low　temperature　climate.