In order to obtain the anatomical basis of transferring the anterior interosseous nerve to repair the injury of thenar or ulnar nerve at the wrist level, ten fresh cadaveric forearms were dissected. The pronator quadratus branch of the median nerve was (1.5 +/- 0.4) mm in diameter with (866 +/- 144) nerve fibers. The recurrent branch of median nerve was (1.7 +/- 0.3) mm in diameter with (1,120 +/- 97) nerve fibers. The deep branch of ulnar nerve was (2.1 +/- 0.4) mm in diameter with (1,318 +/- 120) nerve fibers. To repair the thenar recurrent branch, nerve graft should be used to bridge between the distal end of the anterior interosseous nerve and the origination of the recurrent branch. The deep branch of the ulnar nerve could be repaired by direct suture after being dissected proximally. In patients, the technique was applied to repair 17 cases of injury of thenar branch and 3 cases of injury of deep branch of ulnar nerve. Among them, seventeen cases were followed up from 2 to 7 years. On electromyogram it was normal in 10. The myodynamia was restored in different degree: M2 in 2, M3 in 5, M4 in 7, M5 in 3. The procedure of the operation and the matters needed attention during the operation were discussed.