Abstract: Disclosed are a chain link, a chain conveyor, a filling machine, and a package-flap folding method. The chain conveyor comprises a hinge part and a support part; the support part is fastened with a blade for clamping and pushing a package; the blade divides the support part into a rectangular front support part and a rear support part; multiple chain links can be hinged to form an annular chain, and the distance between the blades of two neighboring chain links in a straight line segment equals to the width of the package; the length of the support surface of the front support part equals to or is slightly smaller than the distance between an flap at the end to the rear side surface of the package; the rear end surface of the rear support part forms the guiding surface for guiding the folding of the flap at the end.