【Abstract】 Objective To investigate the feasibility of transpositional anastomosis of C4 anterior trunk and accessory nerve for functional reconstruction of the trapezius muscle so as to provide theoretical basis of repairing accessory nerve defects. Methods Thirty-six adult male Sprague-Dawley rats (weighing 200-250 g) were randomly divided into the experimental group (n=18) and control group (n=18). The transpositional anastomosis of C4 anterior trunk and accessory nerve was performed in the left sides of experimental group; the accessory nerve was transected in the left sides of control group; and the right sides of both groups were not treated as within-subject controls. The electrophysiological and histological changes of the trapezius muscle were measured. The values of the latencies and amplitudes of compound muscle action potential (CMAP) were recorded in the experimental group at 1, 2, and 3 months; the latency delaying rate, amplitude recovery rate, and restoration rate of muscular tension were caculated. The counts of myelinated nerve fibers from distal to the anastomotic site were analyzed. The transverse area of the trapezius muscle was also measured and analyzed in 2 groups. Meanwhile, the muscles and nerves were harvested for transmission electron microscope observation in the experimental group at 1 and 3 months. Results As time passed by, the experimental group showed increased amplitudes of CMAP, shortened latencies of CMAP, and improved muscular tension. At 3 months, the amplitude recovery rates were 63.61% ± 9.29% in upper trapezius muscle and 73.13% ± 11.85% in lower trapezius muscle; the latency delaying rates were 130.45% ± 37.27% and 112.62% ± 19.57%, respectively; and the restoration rate of muscular tension were 77.27% ± 13.64% and 82.47% ± 22.94%, respectively. The passing rate of myelinated nerve fibers was 82.55% ± 5.00%. With the recovery of innervation, the transverse area of the trapezius muscle increased, showing significant differences between experimental group and control group at different time points (P lt; 0.05). The transmission electron microscope showed that the myotome arranged in disorder at 1 month and tended to order at 3 months. Conclusion Transpositional anastomosis of C4 anterior trunk and the accessory nerve can effectively reconstruct the function of the trapezius muscle of rats.