Objective To analyze the clinical features and etiology of brachial amyotrophic diplegia and raise the awareness of this disease. Methods Analyze the clinical features and etiology of the disease by carefully asking the history, making physical examination and clinical electric neurophysiology examination and combining with the literature review. Results The patients with brachial amyotrophic diplegia have the features that the ends of their both upper limbs are significantly weak and the muscles of their bilateral upper limbs are significantly atrophied, with little or no functional impairment of the legs. However, compared with classical upper limb onset amyotrophic lateral sclerosis, this disease makes slower progress and is rarely found on women. The etiology may be related to gene mutation. Conclusion The analysis of the clinical features and etiology of brachial amyotrophic diplegia has a significant value in its screening and early clinical diagnosis.