Objective To observe the effect of motor nerve baby-sitting and different babysitting stages on nerve regeneration in nerve root re-implantation for brachial plexus avulsion injury.Methods Twenty-four SD rats were used to induce the brachial plexus avulsion injury.C5-7 roots were avulsed and C6 anterior root was re-implanted to the spine cord via a posterior approach.Branches erupting from C6 and the branches affiliated to the musculocutaneous nerve were cut away via an anterior approach.Re-implanted C6 anterior root was connected singly with musculocutaneous nerve.After that,the end of one branch of medial pectoral nerve was sutured to the lateral musculocutaneous nerve.The animal was divided into persistence motor nerve baby-sitting group (Group A,n =12) and protophase motor nerve baby-sitting group (Group B,n =12) according to the random number table.Electrophysiological evoked potential,muscle wet weight and muscle fiber cross-sectional area were measured at postoperative 2 and 3 months.Results At postoperative 2 and 3 months,the restoration rates of motor evoked potential in Group A [(12.2 ± 3.3) ％ and (15.1 ± 3.5) ％] revealed significant differences from these in Group B [(30.1 ±4.2)％ and (54.8 ±9.6)％] (P ＜0.01),the restoration rates of muscle wet weight in Group A [(75.9 ± 5.3) ％ and (92.7 ± 8.6) ％] were similar with (76.4 ± 7.3) ％ and (94.3 ± 4.4) ％ in Group B (P ＞ 0.05),and the restoration rates of muscle fibrin cross section area in GroupA [(74.4±5.5)％ and (88.5±7.5)％] were similar with (76.9±6.7)％ and (92.9± 3.5) ％ in Group B (P ＞ 0.05).Conclusions Motor nerve end-lateral baby-sitting can improve functional restoration of the skeletal muscle in the early stage after nerve root re-implantation,but prevent functional restoration of skeletal muscle in the late stge.On the contrary,protophase motor nerve babysitting avoid the inhibitory effect in the late stage,which gains better restoration rate of muscle motion evoked potential.