Abstract: Objective To investigate the effects of preoperative respiratory exercise on respiratory function during anesthesia recovery period in morbidly obese patients. Methods A total of 70 morbidly obese patients who were scheduled to undergo laparoscopic bariatric surgery were randomly divided into two groups (n=35): an exercise group (Group T) and a control group (Group C). Group C was treated with routine preoperative care methods after admission. Group T was given preoperative respiratory exercise on the basis of the Group C for two weeks. The blood gas of the radial artery was analyzed before oxygen inhalation (T₀), after tracheal intubation (T₁), at 10 min after pneumoperitoneum withdrawal (T₂), before extubation (T₃), at 10 min of oxygen inhalation after extubation (T₄), and before discharging from the post anesthesia care unit (PACU) (T₅). The partial pressure of carbon dioxide (PaCO₂) and pH were recorded, and the oxygenation index (PaO₂/FiO₂) was calculated at six time points. The times from the end of the operation to the extubation of tracheal tube and the length of stay in PACU were recorded. After extubation, we also recorded the time for SpO₂ decreased from 99% to 92% with air and the time for SpO₂ increased from 92% to 99% after oxygen inhalation. Meanwhile, the number of patients with PaO₂/FiO₂＜300 mmHg at T₃, T₄, and T₅ and the occurrence of adverse events in PACU were recorded. Results Compared with Group C, PaO₂/FiO₂ was increased obviously(T₃, T₄, T₅), the time from the end of the operation to the extubation of tracheal tube, the length of stay in PACU and the time for SpO₂ increased from 92% to 99% after oxygen inhalation were significantly shorter, the time for SpO₂ decreased from 99% to 92% with air was obviously longer, the incidence of PaO₂/FiO₂＜300 mmHg at T₅ was decreased significantly (P＜0.05). There was no significantly difference between the two groups in PaO₂/FiO₂ at T₀-T₂, PaCO₂ and pH at all time points, and the incidence of adverse events in PACU (P＞0.05). Conclusions Preoperative respiratory exercise can effectively improve oxygenation and promote the recovery of respiratory function during anesthesia recovery period in morbidly obese patients. It is worthy of clinical application.