Background & Objectives：Previous studies of the high-intensity interval training (HIT) describe a frequent occurrence with improvement in aerobic capacity and blood lipid. Further, a numerous amount of research has been conducted on the effect of hypoxic condition for increasing exercise economy. However, how hypoxia impacts exercise effectiveness is elusive. Therefore, the aims purpose of this study were: (1) to observe the effects of short-term HIT on aerobic capacity and blood lipid, and (2) to examine whether hypoxic condition had a synergistic effect on improving health outcomes in young sedentary women. Methods：62 healthy female college students in sedentary lifestyle (age: 21.9 ± 2.8 years old, V̇O2max: 25.91 ± 4.51mL·kg-1·min-1) were recruited and randomized into normoxic high-intensity interval training group (N-HIT), high-intensity interval group under stable hypoxia simulated at 2500m (HS-HIT), high-intensity training group under changeable hypoxia simulated at 2500-3400m (HC-HIT) or non-exercising control group (CON). They performed 4 weeks of high-intensity interval training, which included 80 repetitions of 6 s maximal cycling exercise interspersed with 9 s recovery three times a week. Peak oxygen uptake (V̇O2peak), blood lipid, serum fasting glucose and lipids including triglycerides, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were assessed before and after the intervention. Heart rate, blood oxygen saturation (SpO2) and ratings of perceived exertion (RPE) were measured at each training session. Habitual physical activity and dietary behavior were monitored during the experiment. A two‐way ANOVA with repeated measures on time was used to examine the changes in outcomes and training period. Partial eta squared (η2) was used as effect size to measure the main and interaction effects. Results：Compared to CON, participants in all the three training groups improved their V̇O2max by different rates (N-HIT: 3.6%; HS-HIT: 8.3%; HC-HIT: 11.9%). However, only significant increases in V̇O2max were found in both hypoxic groups (HS-HIT: 27.8 ± 3.5mL·kg-1·min-1 to 30.0 ± 3.2mL·kg-1·min-1, p < .001 and HC-HIT: 26.4 ± 5.0mL·kg-1·min-1 to 29.3 ± 4.0mL·kg-1·min-1, p < .05). After intervention, there were no significant changes in blood lipid and serum variables. The key findings in this study were that both short-term normoxic and hypoxic exercising group improved aerobic capacity compared to the non-exercising control group, with hypoxic effect showed a significant improvement in this alteration. Conclusion：4 weeks of HIT improved aerobic capacity in sedentary young women. The hypoxic groups, but not the normoxic group, experienced greater rise in V̇O2max under the same exercise levels.