A hands-free breast pump system uses an advanced air bag for excellent contact between the air bag and breast so that a vacuum near the nipple can be guaranteed. The breast pumping and non-pumping condition can be easily converted by inflation and deflation of air bag using a computer-controlled microsystem. These properties not only make breast-pumping hands-free, but also allows the wearer to keep her clothing and bra on. The automatic control of breast milk expression also realizes hands-free breast milk pumping in public or during sleep. The control of pump time and duration can be programmed in a program or in an app. The breast milk expression system can be used independently, or together with a bra, or a shirt. The system disclosed in this patent can also simulate breast milk expression by a real baby by using a pulsing pressure in the air bag, which can squeeze the nipple periodically according a predetermined program.
