Objective To investigate the effects of exposure to 32% oxygen-68% nitrogen (mixed gas) with different protocols on the lung function, blood gas indicators and inflammatory factors in rats undergoing fast ascent. Methods Thirty male SD rats were randomly divided into 5 groups (n＝6): normal control group, group 1 (rats were pressured with mixed gas at 40 m for 4 h, followed by rapid decompression, and lung function was detected at 0, 3 and 24 h after decompression), group 2 (the hyperbaric exposure protocol was the same as that in group 1, but rats were sacrificed immediately after decompression, and then blood was collected for detection of the blood gas indicators, inflammatory factors ［interleukin 1β, tumor necrosis factor α, and transforming growth factor β］ and oxidative stress indicator ［4-hydroxynonenal］), group 3 (the hyperbaric exposure protocol was the same as that in group 1, but rats were exposed to normobaric 100% oxygen for 30 min after decompression. After the examination of the lung function, rats were sacrificed, and blood was collected for the examination of the blood gas indicators, inflammatory factors and oxidative stress indicator), and group 4 (rats were exposed to 100% oxygen at 7 m for 30 min, then to mixed gas at 15 m for 3 h and finally to mixed gas at 40 m for 10 min, followed by rapid decompression. After the examination of the lung function, rats were sacrificed, and blood was collected for the examination of the blood gas indicators, inflammatory factors and oxidative stress indicator). The lung function of the rats was examined by a whole body plethysmography system, blood gas analysis was performed by a blood gas analyzer, and the blood inflammatory factors and oxidative stress indicator of the rats were detected by kits. Results Fast ascent after hyperbaric exposure increased the respiratory rate, shortened the time of inspiration and expiration, increased the peak inspiratory and expiratory flow rates, and elevated the minute ventilation. Normobaric oxygen exposure after fast ascent improved the lung dysfunction, but the respiratory resistance was still increased as compared to baseline level. Fast ascent after hyperbaric exposure with oxygen inhalation at shallower water and increase of depth step by step could also cause damage to the lung function, which was characterized by the increase of expiratory and inspiratory resistance. Conclusion In the diving with semi-closed circuit rebreather, fast ascent may cause damage to the lung, which may be improved to a limited extent by short-term oxygen breathing in initial shallow water or normobaric 100% oxygen afetr fast ascent.