An automatic support system for headrest includes a first fastener, a connecting component, a driving rod, a first swinging component, a first sleeve component, and a linear drive device; The linear drive device is pivotally connected to the first fastener and has an output shaft that is capable of linearly sliding, a front end of the connecting component is pivotally connected to the first fastener, the output shaft of the linear drive device and one end of the driving rod are respectively pivotally connected to two spaced positions of a rear end of the connecting component, a front end of the first swinging component is pivotally connected to the first fastener, the other end of the driving rod is pivotally connected to a rear end of the first swinging component, and the first sleeve component is fixed to a headrest and set on the first swinging component detachably.