The invention provides a preparation method for a watermelon peel based edible packaging film. The method comprises the following steps: (1) cleaning and dicing watermelon peel; (2) carrying out blanching treatment; (3) carrying out pulping treatment until the substance subjected to the pulping treatment is pasty, so as to obtain watermelon peel paste; (4) adding water, a thickener and a plasticizer into the watermelon peel paste obtained in the step (3), so as to obtain watermelon peel slurry, wherein the watermelon peel paste contains the ingredients in percentage by mass: 40-80% of the watermelon peel paste, 0.1-1% of the thickener, 0.05-0.50% of the plasticizer and the balance of the water, the thickener contains sodium alginate and/or sodium carboxymethyl cellulose, and the plasticizer contains sorbitol or glycerine; (5) carrying out homogenization treatment for 5-10 minutes at the treatment rate of 10,000-20,000r/min, and then, carrying out degassing treatment and standing, so as to obtain a shaped sizing material; and (6) carrying out casting and drying, and then, carrying out film uncovering, thereby obtaining the watermelon peel based edible packaging film. The invention also provides the packaging film prepared by the method.