The aim of this study was to extend the clinical application of phrenic nerve neurotization in treating brachial plexus avulsion injury, reducing the possible damage on the diaphragm function. Fifty-one male Sprague-Dawley rats and 9 transgenic rats were used in this study. Evaluations including behavioral observation, histology, and electrophysiology study were performed postoperatively. The functional recovery of rats with the end-to-side neurorrhaphy reached 80% of those with end-to-end neurorrhaphy, and the function of diaphragm was preserved. The fluorescence study revealed abundant collateral sprouting of the phrenic nerve axons through the coaptation site in all the experimental groups. The study showed that the end-to-side neurorrhaphy in a helicoid manner and the standard end-to-side neurorrhaphy were effective in the treatment of brachial plexus root avulsion injury with little harm to the function of diaphragm. This will extend the clinical application of phrenic nerve neurotization in treating brachial plexus avulsion injury.