Abstract: Objective To study the effects of deep helium-oxygen saturation diving on the diver's performance.Methods Operational pedormance of the 4 divers was evaluated before and after the 480 m simulated helium-oxygen saturation dive through the access of manipulation,cognitive performance and eye movement.Results No significant differences in the diver's performance could be detected before and after the experiment.Concerning the indices of the diverr's cognitive performance,significant differences could neither be seen in reaction time,while movement time was obviously shortened[(190.25 ± 44.96) × 10-3 s](P =0.047 ) and accuracy of time perception was greatly improved[(73.75 ± 3.86)% ](P =0.044).At the same time,average visual fixation time was obviously shortened ( P =0.064) and latency of eye movement was significantly prolonged[ (764.38 ± 17.77 ) × 10-6s ](P =0.044 ) following the dive.Conclusions Deep simulated saturation dive exposure might accelerate nerve transmission,the mechanism of which required further investigation.The depth-time course set by this simulated dive had little effect on the diver's performance,resulting in no obvious damage to the divers.