Belonging to the field of intelligent control, the invention relates to an automatic tightening intelligent bra, solves the problem of discomfort caused by the long-term tightening state of bras wornby women, and can achieve active adjustment of the tightening degree of the lower part of the bra according to the body posture. An automatic tightening device is installed at a back buckle, a heart position, the side spleen or other parts, and the device is internally equipped with a gyroscope, a battery, a DC deceleration motor, a screw rod tightening mechanism, Bluetooth and a control circuit.When the gyroscope detects that the woman's body is in forward inclining (including side inclining, hypsokinesis, etc.) state, the gyroscope transmits the state and time to the control circuit in realtime, the control circuit makes a comprehensive determination according to the inclining degree and the lasting time, when the inclining degree and the lasting time meet the set requirements, the control circuit can transmit a loosening signal to the DC deceleration motor, the DC deceleration motor can undergo reverse rotation according to the loosening signal and drive the screw rod tightening mechanism to loosen the upper and lower elastic cords, otherwise tighten the elastic cords. The control circuit can be connected to a mobile terminal through Bluetooth, and the body posture parametersand the bra tightening degree can be adjusted through the mobile terminal.