The invention belongs to the technical field of water-soluble high-polymer dispersion synthesis, and particularly relates to a polymerization method of an anionic polyacrylamide water-drum water dispersion. The in-situ redox initiation method for preparing the polyacrylamide water-drum water dispersion comprises the following steps: carrying out copolymerization reaction to prepare seed polymer SP, and preparing the polyacrylamide water-drum water dispersion from the seed polymer SP, wherein the molecular weight of the seed polymer SP is controlled at (1.5-2.5)*10<6>, the seed polymer contains a tertiary amine group used as a reduction group, and the raw materials for preparing the polyacrylamide water-drum water dispersion contain an oxidant for performing redox reaction with the reduction group to form free radical. Thus, the invention ensures the prepared product to have high flowability, high storage stability and high molecular weight; and meanwhile, the invention does not need special heat transfer and mixing equipment, thereby greatly lowering the preparation cost.