A polymer nano / micro particle additive is prepared from a main monomer and functional monomers by copolymerization. The functional monomers contain carboxylic group, sulfate group, sulfonate group, phosphate group, phosphite group, silane functional group, silicon hydroxyl functional group, and quaternary amine, quaternary phosphonium and tertiary sulfur functional groups; and the polymer nano / micro particle additive is a dry powder, or an aqueous dispersion. Under certain circumstances, the polymer does not contain main monomer but necessarily contains the above functional monomers. By introducing functional groups or anaphase modification, the polymer nano / micro particles have the effects of promoting hydration and nucleation of cement and greatly improving the early hydration rate of cement, so as to achieve improve the early strength of the cement-based materials and improve the toughness of cement-based materials.