Abstract： Objective To investigate effects of simulated heliox diving on physiology,psychology and blood and urine indices in divers at different high altitudes,and also to assess medical support profiles for the simulated heliox diving at different high altitudes.Methods In the dual-purpose hyperbaric and hypobaric chamber complex,4 divers conducted a series of simulated dives for a succession of 9 days at various altitudes and under different simulated environmental conditions:the 30 m dive at an altitude of 3000 m,the 30 m dive at an altitude of 4000 m,and the 30 m and 50 m dives at an altitude of 5200 m.Various physiological indices,such as vital signs,cardiovascular function,CNS function and psychological state,as well as biochemical and immunological indices of the divers were monitored during different stages of the experiment.In the mean time,clinical observations were also made.Ultrasonic Doppler bubble detection was made during the whole process of decompression.Results The 4 divers completed all the experimental items as specified in the plan.In the simulated high altitude environments,all the divers displayed acute slight altitude disease to a more or less extent.The blood pressure of 1 diver elevated,another diver developed fever and still another diver had head injury.No decompression sickness occurred,in the process of decompression and after decompression.However,all of the divers were affected by transient high temperature of the chamber and 1 diver felt numb in the finger.Conclusions The experiment showed that the medical support profile and monitoring systems were feasible and the diving experiment was safely completed.