The invention discloses a self-adaptive automobile rear sunshade. The sunshade comprises a reel arranged in a frame, wherein a rear window is arranged in the reel, the reel is arranged at one side ofthe rear window, a shade cloth is wound on the reel, a first movable cavity and a second movable cavity are formed in the two sides of the rear window, the second movable cavity and the first movablecavity are formed in the frame, the two ends of the reel are fixedly connected with rotating shafts, one of the rotating shafts is rotationally connected with the interior of the first movable cavity,an upper baffle is fixedly connected under the rotating shaft, and a convex lens is arranged on the side, close to the rear window, of the interior of the first movable cavity. According to the sunshade, under the irradiation of sunlight, through the focusing effect of the convex lens, with the cooperation of the reaction of memory metal to temperature, the reel is separated from being bound andcan freely rotate; and under the action of gravity, the shade cloth wound on the reel can be naturally scattered, light rays can be shielded, and a user does not need to manually add the shade cloth.