Abstract：Polyether-modified poly(aspartic acid) superplasticizer（PEMPASP）was synthesized using polysuccinimide (PSI) and polyetheramine M2005 (M2005) as materials. FTIR was used to characterize the PEMPASP. The effects of different superplasticizers and their dosage on the fluidity and flexural strength of cement pastes were discussed and the corresponding mechanism of PEMPASP superplasticizer was studied by TOC, Zeta potential, XRD and TG-DSC. The results showed that when the molar ratio of PSI and M2005 was 1: 0.14 and the dosage of 0.35% of cement, the fluidity of cement pastes mixed with PEMPASP was 189% higher than that of cement paste mixed with PASP, and at dosage of 0.25% the flexural strength of concrete increased by 15.6% compared with that of blank cement and 17% higher than that of cement mortar containing PASP. The introduction of long-chain polyether into PASP molecules changes the charge density and the side chain structure of PEMPASP, which leads to change of the electrostatic effect and steric effect of the superplasticizer on the cement particles. The adsorption, dispersion and the hydration of cement are improved, and then the comprehensive performance of superplasticizer is improved.