Objective To explore the anatomical basis for the flexor pollicis brevis branch of median nerve transfer to the deep branch of ulnar nerve.Methods Eight fresh upper limb were dissected and observed.The specimen were dissected under the loup.Observed the number of the flexor pollicis brevis branch and measured the distances from pisiform bone to the flexor pollicis brevis branch.Then the transfer operation on the cadaver were imitated.After the anastomosis was completed,the stumps of the nerves were sectioned and stained with HE.The crossing-sectional area and the density of nerve fiber were obtained by Image-Pro Plus version 6.0,then the number of the nerve fiber were calculated.The data analyzed by SPSS 17.0.Results The flexor pollicis brevis branch constantly appear,there were two branches in 2 specimens,one branch in 6 specimens.The flexor pollicis brevis branch could transfer to the deep branch of ulnar nerve by end-to-end surture without tension.The regeneration distances was (37.3 ± 5.76) mm.The crossing-sectional area were (0.0575 ± 0.0086)mm2 and (0.2039 ± 0.0396)mm2,the number were (492.50± 62.62) and (1651.13± 79.01),the density were (8781.4246 ± 1676.2894)/mm2 and (8371.1592 ± 1677.6509)/mm2 in the flexor pollicis brevis branch and the deep branch of ulnar nerve,respectively.There were no significant differences in the density of the nerve fiber between the donor and recipient nerve (P ＜0.05).But there were differences in the crossing-sectional area and number of the nerve fiber(P ＜ 0.05).Conclusion The flexor pollicis brevis branch transfer to the deep branch of ulnar nerve can provide a short regenerating distance,but can supply a part of recipient nerve to reinnervate.