The invention discloses a method for preparing edible gelatin by means of freshwater fish skin. The freshwater fish skin is used as a raw material, and gelatin products are prepared by all unit processes such as degreasing, performing alkali treatment, performing acid treatment, digesting, centrifuging and drying. The edible gelatin is prepared from the freshwater fish skin, leftover fish skin inaquatic product processing is fully used, the pollution of by-products and waste to environment is reduced, and economic benefit is improved; and the gelatin of the freshwater fish skin is extracted by low-concentration acid and alkali treatment and hot water extraction methods, the process is simple, the operation is convenient, the quality of the prepared products is high, and the application range is extensive.