In this paper, superplasticizer was synthesized from waste plexiglas and sodium allysulfonate (WPS). Poly(methyl methacrylate-co-ethyl acrylate) grafling sodium allysulfonate (PMMA-g-AS) was prepared through reactive extrusion in self-single screw extruder and hydrolysis reaction. The structures of the WPS were characterized by FT-IR spectrometer. The results show that structures of the WPS are clear. Properties of WPS and traditional naphthalene sulfonated formaldehyde condensates (FDN) were investigated, when water-cement ratio (W/C = 0.29) and the dosage of superplasticizer is 0.6 wt.% of cement, water reducing rate of mortar is 22.1%, which is 7.3% higher than that of FDN. BWP of the mortar of WPS is 1.4%. In addition, the compressive strengths of mortar of 3 d, 7 d and 28 d are higher than that of FDN, respectively, indicating that over-all performance of WPS reaches the standard of superplasticizer and its ratio of performance to cost is higher than FDN.