An under-screen support structure and a display device. The under-screen support structure is configured to support a rollable and slidable display screen (6) in the display device, and includes a sliding middle frame (1), a rotating shaft (2) and a support chain (3). The rotating shaft is mounted on the side of the sliding middle frame facing a rollable and slidable portion of the display screen, and the rotating shaft is transmittingly connected to the display screen by means of the support chain. The support chain includes a plurality of support strips, the extension direction of the support strips is parallel to the axis of the rotating shaft. The cross section of each support strip perpendicular to the axis of the rotating shaft is trapezoidal, and the size of the side facing away from the rotating shaft is greater than that of the side close to the rotating shaft.