The invention discloses an automatic clamp for a semicircular workpiece with a hole. The automatic clamp for the semicircular workpiece with the hole comprises a feeding device and a clamp body. The clamp body comprises a clamp seat, two clamping strips installed on the clamp seat in a bilaterally symmetrical mode, a reset spring and a limiting mechanism. The middle portions of the two clamping strips are connected with the clamp seat in a rotating mode. The reset spring is connected between the tail portions of the two clamping strips. The two clamping strips can only be mutually unfolded relative to an initial position and cannot be folded under the limitation of the limiting mechanism. The head portions of the two clamping strips are provided with protruding clamping structures. The automatic clamp for the semicircular workpiece with the hole is simple in structure, automatic centering, automatic feeding, automatic adjusting and clamping of the workpiece can be completed just through one cylinder, control is easy and convenient, the automatic clamp is suitable for automatically feeding and clamping workpieces under the condition that the material supply directions, such as an outlet of a vibrating disk, are definite, locating is rapid, and the efficiency is high.