Objective To investigate the anatomical evidence of low end-to-side anastomosis of median nerve and ulnar nerve in repair of Dejerine Klumpke type paralysis or high ulnar nerve injury. Methods Twelve formaldehyde anticorrosion specimens (24 sides) and 3 fresh specimens (6 sides) were observed. There were 9 males (18 sides) and 6 females(12 sides). The specimen dissected under the microscope. S-shape incision was made at palmar thenar approaching ulnar side, the profundus nervi ulnaris and superficial branch of ulnar nerve were separated through near end of incision, and the recurrent branch of median nerve and comman digital nerve of the ring finger were separated through far end of incision. The distances from pisiform bone to the start point of the recurrent branch of median nerve, and to the start point of comman digital nerve of the ring finger were measured. The width and thickness of the profundus nervi ulnaris and superficial branch of ulnar nerve, and the recurrent branch of median nerve and comman digital nerve of the ring finger were measured, and the cross-sectional area was calculated. The number of nerve fiber was determined with HE staining and argentaffin staining. Results The crosssectional area and the number of nerve fiber were (2.46 ± 1.03) mm2 and 1 305 ± 239 for the profundus nervi ulnaris, (2.62 ± 1.75) mm2 and 1 634 ± 343 for the recurrent branch of median nerve, (1.60 ± 1.39) mm2 and 1 201 ± 235 for the superficial branch of ulnar nerve, and (2.19 ± 0.89) mm2 and 1 362 ± 162 for the comman digital nerve of the ring finger. There were no significant differences (P gt; 0.05) in the cross-sectional area and the number of nerve fiber between the profundus nervi ulnaris and the recurrent branch of median nerve, between the superficial branch of ulnar nerve and the comman digital nerve of the ring finger; and two factors had a l inear correlation (P lt; 0.05) with correlation coefficients of 0.68, 0.66 and 0.56, 0.36. The distances were (36.98 ± 4.93) mm from pisiform bone to the start point of the recurrent branch of median nerve, and (28.35 ± 6.63) mm to the start point of comman digital nerve of the ring finger. Conclusion Low end-to-side anastomosis of median nerve and ulnar nerve has perfect match in the cross-sectional area and the number of nerve fiber.