The effects of large dose methylcobalamin injection on diabetic peripheral neuropathy in patients were observed to observe the subjective symptom of diabetic perpheral neuropathy (DPN) patients and detect the motor nerve conduction velocity (MCV) and sense nerve conduction velocity (SCV). Fifteen patients were received large dose methylcobalamin injection for two weeks as treatment group, another eleven patients were received muscular injection VitB1 100mg/d, VitB12 500ug/d for two weeks as control group. After 2 weeks treatment the subjective symptoms and signs were significantly improved with a total effective rate of 82.9% in the treatment group however the effective rate only has 52.0% in the control group. The result has obvious difference in statistics nerve MCV in median common peroneal nerve, SCV in median and superficial peroneal nerve were improved significantly in the treatment group and no such changes were observed in the control group. So, large dose methylcobalamin is an effective and safe agent for treatment of diabetic peripheral neuropathy. The effects of large dose methylcobalamin injection on diabetic peripheral neuropathy in patients were observed to observe the subjective symptom of diabetic perpheral neuropathy (DPN) patients and detect the motor nerve conduction velocity (MCV) and sense nerve conduction velocity (SCV). Fifteen patients were received large dose methylcobalamin injection for two weeks as treatment group, another eleven patients were received muscular injection VitB1 100 mg / d, VitB12 500ug / d for two weeks as control group. After 2 weeks treatment the subjective symptoms and signs were significantly improved with a total effective rate of 82.9% in the treatment group however the effective rate only has 52.0% in the control group. The result has obvious difference in statistics nerve MCV in median common peroneal nerve, SCV in median and superficial peroneal nerve were improved significantly in the treatment group and no such changes were observed in the control group. So, large dose methylcobalamin is an effective and safe agent for treatment of diabetic peripheral neuropathy.