Introduction: Developing a practical training model that mimics altitude training will provide more information for coaches, athletes and sport sciences team in designing a more effective training schedule. This study was conducted to explore the short-term wearing a hypoxic training mask effect on respiratory muscle strength and cycling performance in triathletes. Methods: A total of 13 triathletes were recruited. The matched pair grouping method was adopted to divide the triathletes by their height, body weight and maximal oxygen consumption (VO2max) into a control group (168.3 ± 2.2 cm, 63.2 ± 2.7 kg, 51.2 ± 4.0 ml/kg/min, n=5) and training mask group (169.0 ± 2.6 cm, 63.4 ± 2.5 kg, 52.2 ± 3.3 ml/kg/min, n=8). A single-blind method was employed to administer a 4-week intervention, in which the triathletes were asked to wear a training mask while training. The triathlete’s body composition, maximal respiratory muscle pressure, functional threshold power (FTP), and VO2max were measured before and after the intervention. In addition, athletes were asked to fill out a three-day physical activity log and perceived exertion rating log during the intervention. Results: After the intervention, the VO2max was significantly enhanced in both groups. The training mask group showed significantly higher post-training maximal expiratory pressure (PEmax) than pre-training after 4-week intervention. However, the FTP of the training mask and control groups were not different. The percent changes in fat mass and muscle mass for the training mask group were more favorable than those for the control group, attaining significant between-group differences (p = .039 and .014, respectively). Conclusion: Our study demonstrates that the four weeks exercise training significantly enhanced maximal oxygen consumption in these young triathletes. In addition, exercise training combined with the hypoxic training mask could further generate improvement in maximal expiratory pressure and body composition.