Abstract： Objective To explore effects of 40 m repetitive air dives on humoral immunity in healthy volunteers. Methods Sixteen healthy male volunteers experienced 6-time 40 m-35 min simulated air dives for 3 consecutive days. Eight of them took trilogy antioxidants (vitamin C 1 g/d, vitamin E 2.5 g/d, N-acetylcysteine 8 g/d) orally 1 day before and during 3 days of exposure. Complements, immunoglobulins and stress indices in the serum were measured 1 day before and on 1st, 2nd and 3rd days of exposures respectively. Results Significant increases in the values of IgM, IgA, C3 were observed, 1, 2 and 3 days after exposure (P < 0.05), and increases in CA, IgG were noted, 1, 2 days after exposure respectively (P < 0.05). Adrenocorticotrophic hormone increased following 2nd and 3rd days of exposure (P < 0.05). Increases in cortisol, adrenalin, noradrenaline and dopamine showed no statistical significance. Antioxidants did not significantly affect changes induced by diving when compared with the placebo group. Conclusions Increase in the levels of some humoral immunity indices during or after 40 m of simulated repetitive air dives might not be the result of stresses and oxidative stresses.