Objective: To investigate the characteristics of fat metabolism in rat skeletal muscle after hypobaric hypoxia acclimation. Methods: Sprague-Dawley rats were divided into 3 groups randomly: control group (H0), hypoxic 5-day group (H5), and hypoxic 15-day group (H15). Animals of H5 and 15 groups were exposed to hypobaric hypoxia chamber simulating 5 000 m high altitude for 5 d or 15 d respectively, 23 h per day. H0 group stayed outside of chamber. The level of fatty acid oxidation and uptake, and glucose oxidation were examined, and the level of non-esterified fatty acids (NEFA), ATP and phosphocreatine (PCr) were also assayed in rat skeletal muscles. Results: The contents of ATP and PCr in H5 group were lower than those in H0 and H15 groups (P<0.05), while there was no significant difference between H0 and H15. Compared with H0, the blood NEFA level in all hypoxia groups was increased significantly (P<0.05). The muscle NEFA level in H15 group was greatly higher than that in H0 and H5 groups. The rates of fatty acid oxidation and uptake in H15 group were significantly higher than those in H0 and H5 groups (P<0.05), and the rate of glucose oxidation in all hypoxia groups was significantly decreased than that in H0 group (P<0.05). Conclusion: It is concluded that the enhanced fat oxidation may be one of the mechanisms in the maintenance of energy homeostasis after hypobaric hypoxic acclimation. Methods: Sprague-Dawley rats were divided into 3 groups randomly: control group (H0), hypoxic 5-day group (H5), and hypoxic 15- day group (H15). Animals of H5 and 15 groups were exposed to hypobaric hypoxia chamber simulating 5 000 m high altitude for 5 d or 15 d respectively, 23 h per day. H0 group stayed outside of chamber. The level of fatty acid oxidation and uptake, and glucose oxidation were examined, and the level of non-esterified fatty acids (NEFA), ATP and phosphocreatine (PCr) also also assayed in rat skeletal muscles. Results: The contents of ATP and PCr in H5 group were lower than Those with H0 and H15 groups (P <0.05), while there was no significant difference between H0 and H15. Compared with H0, the blood NEFA level in all hypoxia groups was significantly significantly (P <0.05). The muscle NEFA level in H15 group was greatly higher than that in H0 and H5 g The rates of fatty acid oxidation and uptake in H15 group were significantly higher than those in H0 and H5 groups (P <0.05), and the rate of glucose oxidation in all hypoxia groups was significantly decreased than that in H0 group (P < 0.05). Conclusion: It is concluded that the enhanced fat oxidation may be one of the mechanisms in the maintenance of energy homeostasis after hypobaric hypoxic acclimation.