Provided are a device for simulating a full-scale pile-sinking process of a static pressure pile by air bag preloading and a test method thereof. The device comprises a frame, a beam, a hydraulic jack, a model box, a model pile, a first sand layer, an undisturbed soil mass, a second sand layer, a rubber pad, a forcing air bag, a counter-force steel plate, a model box top cover, a forcing pipe, a pressure relief pipe, a steel casing and a control system. The first sand layer, the undisturbed soil mass, the second sand layer, the rubber pad, the forcing air bag and the counter-force steel plate are laid in the model box in sequence; and the steel casing passes through the model box top cover, the counter-force steel plate, the forcing air bag and the rubber pad in sequence and then reaches a bottom portion of the second sand layer.