Several studies have reported the detrimental impacts of hypoxia exposure on sleep. Chinese Kunlun Station (altitude 4087 m) is located at Dome A, the highest point on the Antarctic ice sheet and one of the most extreme environments on Earth. This study investigated alteration of sleep, breathing and mood status in healthy expeditioners at Kunlun Station at Dome A. The study examined 10 male volunteers of the inland transverse party to Kunlun Station during the 31st Chinese National Antarctic Research Expedition, and valid data from eight volunteers were analyzed. Sleep structure, breathing patt and mood were monitored using portable polysomnography (PSG) and profile of mood state (POMS) at two time points: (1) at Zhongshan Station (10 m) before departure to Kunlun Station; (2) on nights 12 –13 of residence at Kunlun Station.Slow-wave sleep (Stage 3 non-rapid eye movement) was markedly reduced at Kunlun Station (P < 0.01). Total sleep time, sleep efficiency and sleep latency showed no significant changes. Total respiratory events (P < 0.05), apnea/hypopnea index (AHI) (P < 0.05) and hypopnea index (P < 0.01) substantially increased at Kunlun Station. The most common respiratory disorder was periodic breathing, occurring almost exclusively during non-rapid eye movement sleep. The oxygen desaturation index increased markedly (P < 0.05), while noctal oxygen saturation dramatically fell at Kunlun Station (P < 0.05). Vigor scores decreased at Kunlun Station (P < 0.05). Expeditioners exhibited reduced slow wave sleep, induced periodic breathing, decreased oxygen saturation and decreased vigor at Kunlun Station.