The invention discloses an umbrella-shaped unfoldable antenna capable of folding and unfolding reflecting surfaces synchronously. The umbrella-shaped unfoldable antenna mainly comprises a supporting disk, a supporting rod, 12 reflecting surfaces, a driving part and reflecting surface position-changing devices. The driving part is composed of 2 motors, 2 couplings, a No.1 lead screw, a No.2 lead screw, 12 long connecting rods, 12 short connecting rods, a large sliding disk, a small sliding disk. The reflecting surface position-changing devices are evenly distributed on the circumferential edgeof the supporting disk, and each comprise a telescopic shaft, a straight sliding block, an oblique sliding block, an inclined track and straight track. One end of each long connecting rod is connectedwith the large sliding disk, and the other end is connected with the corresponding reflecting surface by means of a variable posture ball. One end of each short connecting rod is connected with the small sliding disk, and the other end is connected in the straight track in the middle part of the long connecting rod by means of a mobile pair. The reflecting surfaces are mounted on the telescopic shafts of the reflecting surface position-changing devices, so as to achieve the purpose of adjusting attitudes of the reflecting surfaces by means of changes of the reflecting surface position-changing devices. The umbrella-shaped unfoldable antenna can realize the automatic and synchronous folding and unfolding of the antenna reflecting surfaces, and is conductive to realizing high mobility and good concealment of the antenna.