Objective To investigate the effects of positive pressure ventilation combined with leukotriene receptor antagonists on immune function in children under 6 years of age with obstructive sleep apnea（OSAHS）. Methods Ninety children under 6 years old with OSAHS were selected and randomly divided into leukotriene group and combination therapy group（n = 45）in our hospital from January 2019 to January 2020. The levels of T lymphocyte subsets，NK cell counts，and SaO2 levels in the two groups were compared. To examine the changes in the levels of AHI，lat，LHT，IgA，IgG，and IgM in the two groups，the treatment response rate and the incidence of adverse effects were compared between the two groups. Results Children receiving combination therapy had lower levels of CD3+，CD4+，CD8+，lat，LHT，AHI，IgA，IgG，IgM，SaO2 and higher levels of NK than children on leukotrienes（P < 0.05）. The total effective rate of treatment was higher in the combination group（P < 0.05）. Conclusion Positive pressure ventilation combined with leukotriene receptor antagonist could regulate T lympho⁃ cytes and improve NK cells and immunoglobulin factors in children under 6 years of age with OSAHS，which has with significant clinical effects.