The invention relates to a tearable packaging film and a preparation method thereof, and belongs to the technical field of cast films. The raw materials for preparing the tearable packaging film include, by weight, LDPE, LLDPE, HDPE, PP, metallocene polyethylene, a lubricant, a dispersant, an antibacterial agent and a crystallization nucleating agent, wherein the antibacterial agent comprises teapolyphenols and chitin fibers; and the crystallization nucleating agent comprises dibenzylidene sorbitol, p-hydroxybenzoic acid and poly(phenyl 4-methoxyl-4'-acryloyloxybenzoate). The invention also discloses the preparation method of the tearable packaging film. The preparation method comprises the following steps: S1, mixing, and extrusion plasticizing; S2, extrusion casting; S3, calendering setting; and S4, corona, trimming and rolling. The packaging film is convenient to tear.