An airtight sheath for packing a bottle, the airtight sheath made of at least two outer films (101, 102) heat-sealed together and comprising: a first buffering unit comprising a plurality of first air columns, and two distal heat-sealing sides being heat-sealed to terminate two opposite sides of the first buffering unit; a second buffering unit comprising a plurality of second air columns, two opposite sides of the second buffering unit being heat-sealed with the two distal heat-sealing sides of the first buffering unit; a bottom unit comprising a plurality of bottom air columns connected with ends of the plurality of first air columns and second air columns, whereby a packing space is formed by the first and second buffering units (1, 2) and the bottom unit and is open at a top of the sheath for packing a bottle therein, so that the bottom unit and the first and second buffering units (1, 2) cooperatively forming a packing space for packing the bottle therein; and a cover extending from one end of the first buffering unit opposite to the bottom unit and disposed in the packing space, the cover comprising two connecting air columns and at least a lid air column located between the two connecting air columns, each of the connecting air columns and the lid air column respectively having a top portion and a shielding portion bending from the top portion and extending downward to the packing space, the top portion extending and bending from the first air column, a side of each of the connecting air columns opposite to the lid air column being heat-sealed with the first buffering unit, whereby the cover and the first buffering unit cooperatively forming an insertion slot communicating with the packing space for enveloping a neck portion of the bottle. a first buffering unit comprising a plurality of first air columns, and two distal heat-sealing sides being heat-sealed to terminate two opposite sides of the first buffering unit; a second buffering unit comprising a plurality of second air columns, two opposite sides of the second buffering unit being heat-sealed with the two distal heat-sealing sides of the first buffering unit; a bottom unit comprising a plurality of bottom air columns connected with ends of the plurality of first air columns and second air columns, whereby a packing space is formed by the first and second buffering units (1, 2) and the bottom unit and is open at a top of the sheath for packing a bottle therein, so that the bottom unit and the first and second buffering units (1, 2) cooperatively forming a packing space for packing the bottle therein; and a cover extending from one end of the first buffering unit opposite to the bottom unit and disposed in the packing space, the cover comprising two connecting air columns and at least a lid air column located between the two connecting air columns, each of the connecting air columns and the lid air column respectively having a top portion and a shielding portion bending from the top portion and extending downward to the packing space, the top portion extending and bending from the first air column, a side of each of the connecting air columns opposite to the lid air column being heat-sealed with the first buffering unit, whereby the cover and the first buffering unit cooperatively forming an insertion slot communicating with the packing space for enveloping a neck portion of the bottle.