Effects of polycarboxylate (PCE) superplasticizers with different densities of carboxylate groups, functional group contents, molecular weight, and side chain polymerization degrees on the hydration behavior of Portland cement were investigated in this study.The experiments were conducted using a semi-adiabatic calorimeter equipped with a temperature measurement system at 20 ℃.The water cement ratio (w/c) was 0.4, and the PCE dosage used was 0.3%.The ability to delay hydration increased in PCEs with high densities of carboxylate groups, short side chains, and high molecular weight and the presence of methyl acrylate (MA) monomers decreased the hydration rate peak.Nevertheless, the hydration rate peak and hydration temperature peak decreased when the density of the carboxylate groups increased to a certain value, and the hydration age needed to reach these peaks was unchanged.Moreover, PCEs with only a moderate molecular weight had the lowest hydration degree.The second hydration rate peak decreased but appeared in advance when the amount of MA monomers copolymerized with PCEs was increased;the hydration degree also decreased.PCEs only polymerized by methyl allyl polyethenoxy ether (TPEG400) macromonomer had a hydration degree of 69.46%.These results indicate that PCEs affect the hydration of cement paste by absorbing PCE on the surface of cement particles or encapsulating some cement particles to restrain cement hydration.PCEs grafted with MA hydrolyzed to carboxylic and hydroxyl groups, which can both restrain the hydration of cement paste.