The invention provides a hand-held variable-diameter clamp-type Dimocarpus longan girdling machine provided with a semicircle-surface cutter head. The hand-held variable-diameter clamp-type Dimocarpuslongan girdling machine comprises a clamping clip and the semicircle-surface cutter head, wherein the clamping clip comprises a mobile clip body and a fixed clip body, the mobile clip body is provided with handles, joint plates, the semicircle-surface cutter head, an angle adjusting bolt and a force applying handle, and a pin shaft which penetrates through holes formed in the semicircle-surface cutter head and the force applying handle is installed in the force applying handle; angles between the semicircle-surface cutter head and the handles are 90-150 degrees, the angle adjusting bolt is connected with the semicircle-surface cutter head, and by rotating the angle adjusting bolt, the semicircle-surface cutter head rotates around the pin shaft, so that the angles between the semicircle-surface cutter head and the handles are changed; the fixed clip body is provided with the handles, the joint plates and a clamping circle, the diameter of the clamping circle is within a range of 10-150mm, and round holes are formed in the joint plates; a connecting shaft penetrates the round holes formed in the joint plates so that the mobile clip body and fixed clip body of the hand-held clamp-type girdling machine are connected together, and a torsional spring which is arranged between the mobile clip body and the fixed clip body is connected to the handles in a hung mode.