The invention discloses a down jacket liner with an automatic down feather filling function. The down jacket liner comprises front pieces, a rear piece, sleeve pieces, automatic down feather filling zip fasteners and a down feather containing space, wherein the front pieces, the rear piece and the sleeve pieces are stitched, and comprise inner liner cloth close to a down jacket interlayer layer, outer liner cloth close to a down jacket surface cloth layer, and down feather containing spaces which are separated horizontally at equal distances and are located between the liner cloth and the outer liner cloth; the automatic down feather filling zip fasteners are vertically arranged on the outer surfaces of the inner liner cloth of the front pieces, the rear piece, sleeve pieces; down feather filling openings are formed in the two ends of the inner sides of the automatic down feather filling zip fasteners. With the adoption of the manner, the down jacket liner with the automatic down feather filling function realizes that down feather in old down jackets can be directly and repeatedly used; the reutilization manner is portable and any cost is not caused; the operation of a sewing machine is saved, and a user can automatically fill the down jacket at home, so that the down feather filling quantity and down feather varieties can be automatically determined.