Objective To investigate the effectiveness of transferring the ulnaris proper digital nerve of index finger and its dorsal branch to repair the thumb nerve avulsion. Methods Between January 2007 and May 2015, 23 patients with thumb nerve avulsion were treated by transferring the ulnaris proper digital nerve of index finger and its dorsal branch. There were 17 males and 6 females with an average age of 32 years (range, 16-63 years). The injuries were caused by machine twist in 10 cases, electric saw in 8 cases, and sharp article prick in 5 cases. And thumb rotational avulsion amputation happened in 8 cases, thumb incomplete amputation in 2 cases, laceration of thumb palmaris with the thumb nerve avulsion of both sides in 13 caese (7 cases with tendon rupture). The time from injury to operation was 1.0-3.5 hours (mean, 2.2 hours). Results All incisions healed by first intention. Ten cases of thumb reimplantation were successful. All the patients were followed up for 5 months to 2 years and 8 months, with an average of 1 year and 4 months. Two-point discrimination was 3-9 mm (mean, 6.8 mm). According to Society of Hand Surgery standard for the evaluation of upper part of the function, the sensory of the thumb was rated as S4 in 18 cases and \begin{document}${{\rm{S}}_{\scriptsize{3^ + }}}$\end{document} in 5 cases; the sensory at donor sites recovered to S3. Conclusion Transferring the ulnaris proper digital nerve of index finger and its dorsal branch to repair the thumb nerve avulsion is a simple and effective method to restore sensory function of the thumb pulp.