A hollow self-expanding bottom anchor bolt, including a rod body, a wedge, and a liner pipe. The center of the rod body is provided with a hole in the rod body. The rod body includes a bottom end, a middle rod, and an exposed end. There is a wedge inner hole in the center of the center, the wedge includes a wedge head and a base, the outer peripheral surface of one end of the inner liner is connected with the inner peripheral surface of the inner hole of the rod, and the outer peripheral surface of the other end of the inner liner is connected with the inner hole of the wedge. The inner peripheral surface is connected, and the inside of the lining pipe is connected with the inner hole of the rod and the inner hole of the wedge; when installing, insert the above-mentioned anchor bolt into the bottom of the straight hole, hammer or impact the installation cap, so that the wedge pushes the cutter head toward the The hole wall is expanded, and the cutter head is inserted into the straight hole wall to chisel out the broken pieces. While hammering or impacting the installation cap, use the installation cap to input compressed air to blow out the broken pieces. The grout overflows, and the anchor bolts are installed after the grout solidifies. This design not only has good bottom expansion effect, but also has good grouting quality, high durability and high reliability.