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, the bottom unit and the first and second buffering units (1 and 2) cooperatively forming a packing space for packing the bottle therein, characterized in that each of the bottom air columns having at least a sealing node being heat-sealed, the sealing nodes being arranged in alignment with each other, two recessed sealing lines respectively formed at and bending inwardly from opposite end portions of the bottom unit and connecting the distal heat-sealing sides, the sealing nodes and the recessed sealing lines cooperatively enabling the bottom air columns to bend toward the packing space when being inflated, such that the bottom unit functions as a reversed hammock-like cushioning structure for supporting the bottle; and the airtight sheath further comprises a cover extending from one end of the first buffering unit opposite to the bottom unit and disposed in the packing space, 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, the bottom unit and the first and second buffering units (1 and 2) cooperatively forming a packing space for packing the bottle therein, characterized in that each of the bottom air columns having at least a sealing node being heat-sealed, the sealing nodes being arranged in alignment with each other, two recessed sealing lines respectively formed at and bending inwardly from opposite end portions of the bottom unit and connecting the distal heat-sealing sides, the sealing nodes and the recessed sealing lines cooperatively enabling the bottom air columns to bend toward the packing space when being inflated, such that the bottom unit functions as a reversed hammock-like cushioning structure for supporting the bottle; and the airtight sheath further comprises a cover extending from one end of the first buffering unit opposite to the bottom unit and disposed in the packing space, 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.