The invention provides a full-automatic quantitative powder packing unit and a packing method. At present, a manual bagging mode is adopted for most of packing bags in markets, manual opening stitching is not attractive, packing by one person is difficult to implement, opening stitching is not firm, and efficiency is low. The full-automatic quantitative powder packing unit comprises a bag preparing device (1), an opening and taking mechanism (2), a bag loading mechanism (3), a quantitative filling device (4), a manipulator bag-transferring device (5), a pre-guiding device (6), an automatic edge folding device (7), an opening stitching device (8) and a conveying device (9), wherein the bag preparing device is connected with the opening and taking mechanism; the opening and taking mechanismis connected with the bag loading mechanism; the bag loading mechanism is connected with the quantitative filling device; the quantitative filling device is connected with the manipulator bag-transferring device; the manipulator bag-transferring device is connected with the pre-guiding device; and the automatic edge folding device and the opening stitching device are mounted at one end of the pre-guiding device. The full-automatic quantitative powder packing unit is used for a packing machine.