The invention discloses a preparation method of an edible animal collagen casing. The preparation method comprises the following steps: a, material preparation: cleaning and splitting animal skin; b,material treatment: performing alkali treatment on the split animal skin, adding water according to a weight ratio of the animal skin to the water of 1:1, performing enzyme treatment with protease, cleaning the animal skin, and then, performing acid treatment; c, preparation of fiber pulp: cooling the animal skin after acid treatment to be lower than 10 DEG C, cutting up the animal skin by means of dicing, tabletting, chopping and grinding or a combination mode thereof, rolling the cut animal skin into sheets, and extracting silk fiber by means of high pressure filtration; d, preparation of collagen pulp: adding edible cellulose or edible cellulose derivates and grease emulsion while stirring, controlling pH value and water content, and performing uniform mixing and stirring to form a collagen group; e, preparation of casing: freezing the collagen group, performing extrusion to spray a tubular substance, drying the tubular substance, and adding a curing agent and a plasticizing agent for treatment; f: curing and forming: curing and shaping the casing for 6 hours at 82 DEG C; and g: defect detection: detecting whether the casing is broken or not by using a casing detection device.