Abstract: Objective To investigate the role of Methylcobalamin in prevention and treatment of chemotherapy-induced peripheral neurotoxicity(CIPN)in patients with breast cancer by docetaxel. Methods 88 patients with breast cancer by docetaxel chemotherapy were randomly divided into Methylcobalamin treatment group and control group.45 patients were entered in Methylcobalamin treatment group and 43 patients in control group.The Methylcobalamin treatment group patients received Methylcobalamin 500μg with NS 100ml per day for 7 days from the first day treated with docetaxel.The clinical sensory nervous system symptoms and the level of peripheral nerve toxicity were recorded before chemotherapy,after chemotherapy per week.6 months follow-up of patients with symptoms of neurotoxicity were carried out. Results The incidence and severity of CIPN were reduced more significantly in Methylcobalamin treatment group than in control group.The average beginning of peripheral neurotoxicity reaction time in Methylcobalamin treatment group were(16.4±5.2)weeks with docetaxel dosage of(315.8±38.2)mg and lagged far behind that in control group,which were(9.8±3.2)weeks with docetaxel dosage of(210.8±29.2)mg.No significantly difference was found on the time of peripheral neurotoxicity fully restored between two groups. Conclusion Chemotherapy combined Methylcobalamin effectively prevented CIPN in breast cancer patients treated by docetaxel.