Objective To study the features of electrophysiological examination in the carpal tunnel syndrome( CTS). Methods The result of electrophysiological examination of 60 cases of CTS and 60 normal controls were analyzed. Results In the 98 abductor pollicis brevis of affected side in 60 cases of CTS group,39 of which were neurogenic damaded. The sensory and motor conduction of 98 median nerves of affected side in 60 cases of CTS group were all abnormal. Compared with normal control group,the latency of sensory nerve action potentials( SNAP) was prolonged,the amplitude of SNAP was decreased,and the conduction velocity of SNAP was slowed in median nerves of CTS group; and the distal latency of motor conduction was prolonged,the amplitude of compound muscle action potentials was decreased in median nerves of CTS group( all P 0. 05). Conclusion The electrophysiological features of CTS are the slowing of the conduction velocityy of SNAP,the decrease of the amplitude of SNAP and the prolong of the distal motor latency in median nerves,and the neurogrnic damage of abductor pollicis brevis.