The invention discloses an aqueous wallpaper printing medium and a preparation method thereof. The aqueous wallpaper printing medium comprises the following components in parts by weight: 50-80 parts of methyl methacrylate, 10-30 parts of butyl acrylate, 15-35 parts of vinyl versatate, 1-5 parts of acrylic acid, 1-5 parts of hydroxyethyl acrylate, 1-5 parts of N-hydroxymethyl acrylamide, 3-5 parts of active emulsifying agents NRS-10, 10-18 parts of initiating agents, 150-300 parts of deionized water, 0.6-1 part of flatting agents, 0.5-1 part of defoaming agents, 0.2-0.5 part of multifunctional auxiliary agents NP-95 and 3-5 parts of wax emulsions E-8046s. The preparation method of the aqueous wallpaper printing medium comprises the following two steps of: synthesizing the cross-linking type tert-acrylic emulsion of a core-shell structure; and preparing the aqueous medium. The obtained aqueous wallpaper printing medium disclosed by the invention is an environment-friendly aqueous wallpaper printing medium which meets the requirement for safe production, is high in drying speed and can ensure that a wallpaper coating has very good glossiness and abrasion resistance.