Objective: To investigate the phenotype and functional changes of double negative T cells (DNT) in rats with acute high altitude pulmonary edema induced by hypobaric hypoxia, and to explore the potential of DNT cells as treatment or relief for high altitude pulmonary edema. Methods: Normoxic control (NC) and hypobaric hypoxia (HH) groups were established. The proportion, phenotype (CD44, CD62L) and function (IFN-γ, TNF-α, IL-4, IL-10) of DNT cells in lung tissues of rats in NC and HH group were analyzed by flow cytometry. The HH group and HH + TNF-α group were established, and the effects of TNF-α on the differentiation, phenotype and function of DNT cells in lung tissue and spleen of hypobaric hypoxia rats were further analyzed by flow cytometry. Finally, the potential of DNT cell therapy for HAPE was analyzed by adoptive transfer of DNT cells. Results: The proportion of DNT cells in lung tissue of rats in HH group was (1.43 ± 0.20)%, which was statistically significant compared with that in NC group (1.75 ± 0.28)% (P < 0.05). Further detection showed that there was no significant difference in DNT cell phenotype (CD44, CD62L) and some cytokines (IFN-γ, TNF-α, IL-4) between the HH group and the NC group (P > 0.05). However, the level of IL-10 of DNT cells in NC group (2.29 ± 0.20)% was higher than that in NC group (1.57 ± 0.22)% (P < 0.05). By injecting TNF-α into rats in HH group, it was found that the expression level of CD44 in DNT cells in the lungs of HH + TNF-α group (36.22 ± 2.44) was higher than that of HH group (29.75 ± 3.29) (P < 0.05). However, there were no significant differences in DNT cell proportion, CD62L expression and cytokine levels (IFN-γ, TNF-α, IL-4 and IL-10) in lung and spleen between the two groups (P > 0.05). Furthermore, the degree of lung injury in HAPE rats was alleviated by adoptive transfer of DNT cells. Conclusion: Hypobaric hypoxia inhibits DNT cell differentiation and promotes IL-10 secretion, which is not regulated by TNF-α. When compared with CD4? and CD8? T cells, DNT cells secret lower levels of IFN-γ and TNF-α, and higher levels of IL-4 and IL-10 under hypobaric and hypoxia conditions. Moreover, the adoptive transfer of DNT cells alleviated HAPE to a certain extent. These results suggest that DNT cells have the potential to reduce inflammation and relieve pulmonary edema.