OBJECTIVE To find a sensitive index of early injury of the nervous system in lead-exposed workers and to provide a scientific basis for establishing an efficient occupational health surveillance route. METHODS A total of 317 lead-exposed workers (blood lead levels: 26.90∼ 912.80 µg/L, determined with the atomic absorption spectrum) were divided into four groups according to the normal blood lead level (201 µg/L), acceptable upper limit of blood lead (400 µg/L), and diagnostic value (600 µg/L). The motor nerve conduction function was examined and analyzed by one-way ANOVA. RESULTS The distal latency and amplitude of the median nerve were significantly different between groups. The median distal latency of the highest blood lead group (>600 µg/L) was 3.63 ms, which was significantly longer than the average level (3.30 ms), and the median nerve amplitude of the highest blood lead group was 5.63 µV, significantly lower than the average level (7.27 µV). No significant difference was found between different groups in motor conduction velocity. Significant difference was found in ulnar nerve amplitude between groups. The ulnar nerve amplitude of the highest blood lead group was 4.31 µV, significantly lower than the average level (4.87 µV). No significant differences were observed in other parameters between groups. CONCLUSIONS The distal latency and amplitude of the median nerve can be used as a sensitive index for the diagnosis of early subclinical motor nerve injury in lead?exposed workers.