The invention discloses a preparation method of PVDC resin for an inner printed film. The method comprises the following steps: enabling polymerization reaction of 120 to 145 parts by weight of de-ionized water, 70 to 85 parts by weight of vinylidene chloride monomers, 15 to 30 parts by weight of vinyl chloride monomers, 0.1 to 0.5 part of an initiator, 0.05 to 0.3 part of a pH value buffer-conditioning agent, 0.05 to 0.15 part by weight of a dispersing agent, 0.5 to 1.85 parts by weight of a plasticizer, 0.03 to 0.3 part by weight of a lubricant and 0.5 to 2 parts by weight of acrylic acid resin, terminating polymerization reaction after reaction is performed for 38 to 48 hours, removing residual monomers under a vacuum condition, and performing cooling, discharging, centrifugation and drying; adding the plasticizer and the lubricant into a dried material, and performing mixing and aging at 60 to 70 DEG C to obtain a PVDC resin product for the inner printed film. A process is safe and simple, a polymerization reaction process is stable and free of centralized heat release, and a picture of an inner printed packaging film prepared by the product has a strong sense of layering and good brightness and luster.