Objective 　To provide anatomical basis for treating bony mallet finger by absorbable suture tying avulsion fracture fragment. 　Methods　16 fresh adult upper limb specimens were randomly selected, including 16 thumbs, 16 index fingers, 16 middle fingers, 16 ring fingers and 16 little fingers. The important structures of distal phalanx were observed . The distance from the extensor terminal tendon to rear projection line of the distal finger grain and the distance from nail matrix proximal end to the distal tendon terminal and the width of the tendon terminal were measured to design suitable length and width for skin incision.　Results　(1)Tendon insertion width were as follow: thumb (10.72±0.42) mm, index finger (6.14±0.33) mm, middle finger (6.73±0.39) mm, ring finger (5.63±0.37) mm, little finger (4.64±0.38) mm, respectively; (2) proximal distance between tendon insertion and nail matrix were as follow: thumb (1.53±0.12) mm, index finger (1.46±0.08) mm, middle finger (1.48±0.07) mm, ring finger: (1.42±0.07) mm, little finger (1.42±0.08) mm; (3) the distance between the tendon insertion point and the dorsal projection line of the distal finger: thumb (6.12±0.55) mm; index finger (5.03±0.36) mm; middle finger (5.15±0.32) mm; ring finger (4.89±0.36) mm; little finger (4.02±0.24) mm.　Conclusions　When treat bony mallet finger by absorbable suture tying avulsion fracture fragment, we should perform U-shape incision at the distal interphalangeal joint, start from the streakline on the palm side. The width of the incision is 2.0 mm across the tendon insertion, which will not affect the blood supply and can fully expose the operative field.