An autonomous seat system of an automotive vehicle and a performing method thereof are disclosed. The system and method are aimed to reduce discomfort of a passenger due to centrifugal forces resulted from vehicle's turning motion. The system includes a lane prediction unit, a control unit, and a seat adjusting unit. The lane prediction unit is utilized for obtaining lane information in front of the automotive vehicle. According to the lane information the control unit calculates the centrifugal force which the passenger experiences while sitting in a seat of the automotive vehicle, and a seat tilt angle which is required for the seat to compensate the centrifugal force after a predetermined time interval. The seat adjusting unit adjusts the seat to the seat tilt angle after the predetermined time interval so as to reduce or eliminate the ill-effect on the passenger resulted from the centrifugal force.