Objective To study the characteristics of peripheral nerve conduction (PNC) in advanced-stage amyotrophic lateral sclerosis (ALS) patients undergoing mechanical ventilation. Methods The sensory conduction velocity(SCV), motor conduction velocity（MCV）, distal motor latency(DML) and amplitude of compound muscle action potential(CMAP) were determined in three ALS patients undergoing mechanical ventilation. The clinical data and PNC characteristics of the patients were analyzed. Results The 12 motor nerves were abnormal in all the three patients, including absence of responsive wave (66.7%,8/12) , decreased amplitude of CMAP(33.3%,4/12), prolongation of DML(16.7%,2/12) and reduction of MCV(16.7%,2/12). The CMAP amplitude of patients gradually decreased with the progression of disease, and finally led to adverse reactions. The SCV and amplitude of sensory nerve action potential were normal in all the three patients. Conclusion ALS patients undergoing mechanical ventilation may have severely damaged motor nerve conduction, and their sensory nerve is generally not affected, with the specific reason remains to be further studied.