Abstract： Objective To study the effect of the 480 m simulated heliox saturation dive on the mood of divers and to provide evidence for psychological intervention.Methods The mood of the 4 divers exposed to different hyperbaric pressures were evaluated with SAS,SDS,clinical observations and personal interviews.Results The scores of SAS ( r =0.335,P =0.001 ) and SDS ( r =0.235,P =0.025 ) were positively correlated with the atmospheric pressures they exposed to,with a statistically significant difference.No linear correlation could be noted between the exposure duration and divers' mood,also without statistical significance.Although there were no positive detection of mental symptoms,different negative emotional reactions could be noted at various stages of the experiment.Conclusions Heliox exposure seemed to have dynamic effects on the anxiety and depression of divers.Psychological intervention in the divers should be directed in accordance with the divers' main negative emotional reactions at different experimental stages.