The invention relates to a rear-support-type screw anchor structure device and a construction method thereof. The rear-support-type screw anchor structure device comprises a steel pipe, a plurality ofscrew blades and a sleeve valve pipe; the screw blades comprise upper screw steel plates, lower screw steel plates and expansion mechanisms, wherein the upper screw steel plates and the lower screw steel plates sequentially sleeve the steel pipe and are parallel to each other, and the expansion mechanisms are mounted between the upper screw steel plates and the lower screw steel plates; cloth bags or expansion blades are adopted as the expansion mechanisms; and the expansion blades comprise expansion blade main bodies movably mounted between the upper screw steel plates and the lower screw steel plates, and further comprise baffles arranged at the inner ends of the expansion blade main bodies. According to the screw anchor structure device and the construction method thereof, the penetration resistance of a screw anchor can be effectively reduced, and the bearing property is improved.