Size-changeable bra cup

The utility model relates to a size-changeable bra cup, which comprises an outer layer fabric, a thermoplastic rubber lining placed inside the outer layer fabric and an air-filling layer wrapped inside the thermoplastic rubber lining. Sunk holes are arranged on the inner side and the outer side of portions of the thermoplastic rubber lining which are used for wrapping the air-filling layer, the sunk holes with longitudinal depth can not penetrate into the air-filling layer; the air-filling layer is a self-inflatable air cushion, the air-filling layer is connected with an air guiding tube connected with an air valve on the outer layer fabric. The bra cup has the advantages that by adopting the structure that the inner rubber lining is wrapped inside the outer fabric, and that the inner rubber lining which is the thermoplastic rubber lining includes the air-filling layer inside, the bra cup can be changed by changing sizes of the air-filling layer of a finished product according to actual using requirements; meshed sunk holes and air through holes are arranged on a rubber lining body, thereby enabling the bra cup to be lighter and more convenient and attached to breasts preferably when in wearing, and enabling the overall bra cup to be extremely practical.