An automatic warning and breaking system for a vehicle, includes a plurality of cameras, a motion sensor, a data process unit, an alarm unit, a control unit and an adjustor unit. The cameras are for capturing images of objects inside and outside of the vehicle. The motion sensor unit includes at least an acceleration sensor and a gyro sensor, configured for sensing motion of the vehicle. The data process unit is electrically connected to the cameras and the motion sensor unit, configured for processing data from the respective cameras and the motion sensor unit. The alarm unit is connected to the data process unit, configured for giving a warning signal if a data processing result is unsafe. The control unit is configured for generating a control signal based on the warning signal. The adjustor unit is configured for adjusting a break unit of the vehicle based on the control signal.