Graphene oxide (GO) as a new nano-enhancer in cement-based materials has gained wide attention. However, GO is easy to aggregate in alkaline cement mortar with poor dispersibility. This hinders its application in practical infrastructure construction. In this work, GO-M18 polycarboxylate compound superplasticizer (GM) were obtained by compounding the M18 polycarboxylate superplasticizer with GO solution at different mass ratios. The dispersion of GM in alkaline solution was systematically studied. The phases and functional groups of GM were characterized by XRD and FTIR. The effects of GM on the cement mortar hydration and the formation of microstructure were investigated by measuring the heat of hydration, MIP, TG/DSC, and SEM. The results show that the long-chain structure of the M18 polycarboxylate superplasticizer can increase the interlayer spacing of GO and weaken the force between GO sheets. The modified GO can be uniformly dispersed in the cement slurry. GM can accelerate the early hydration process of cement, which can increase the content of Ca(OH) 2 and decrease the grain size. It can optimize the pore size distribution of cement-based materials, increase the density of harmless and less harmful pores, thereby improving mechanical properties. Such methods can transform traditional cement-based materials into stronger, more durable composites, which prolong the life of cementbased materials and reduce the amount of cement used for later maintenance. This provides an idea for achieving sustainability goals in civil engineering.