The invention relates to a preparation method of an enhanced polyacrylamide-series cement grinding aid. The method includes the following steps: performing a water solution free radical polymerization reaction to unsaturated acrylamide and an unsaturated polyether large monomer under the effects of an initiator and a chain-transfer agent, and then adding alkylbenzene sulfonate and modified alcohol amine to prepare the enhanced polyacrylamide-series cement grinding aid. The grinding aid belongs to high-molecular liquid polymer. By means of addition of active functional groups in the molecular chain, the grinding aid significantly increases early and later strength, increases grinding efficiency, improves cement performance and is simple in processes.