The efficacy of uvulopalatoplasty in the treatment of moderate obstructive sleep apnea syndrome (OSAS), which is a symptom of moderate obstructive sleep apnea syndrome (OSAS), is monitored by polysomnography, and the sleep breathing disorder index is between 21 and 50, accounting for about 60-70% of all OSAS patients. The UPPP procedure was performed in 64 cases by expanding the scope of soft palate resection, dissecting the palatal sail gap and removing the fatty tissue therein, and preserving the basic structure and physiological function of the uvula and pharyngeal cavity. 1.Materials and methods: 64 patients with moderate OSAS, 58 males and 6 females, with an average age of 42.2 years, were treated with PSG monitoring of sleep disordered breathing index between 21 and 50 and SaO2>0.85. The operation was performed via nasal cannula with intravenous compound anesthesia. (1) The tonsils were routinely excised bilaterally, and the anterior arch mucosa, tonsillar fossa and posterior arch mucosa were sutured laterally to eliminate the dead space and expand the effective area of the pharyngeal cavity. (2) Use CO2 laser to incise the soft palate mucosa in inverted “U” shape on both sides of the uvula, the highest point of the soft palate incision line is about 1/2 of the length of the soft palate, if the disease is mild, it can be moved down 1-3mm. (3) Dissect the palatal sail gap, remove the submucosal fatty tissue, bluntly separate the muscle tissue to the pharyngeal side, and preserve the palatal sail tensor muscle and palatal sail The mucosa of the pharyngeal surface of the soft palate was incised along both sides of the uvula, and part of the excess mucosa was removed from the lateral wall of the pharynx where it meets the soft palate. (4) The mucosa of the uvula and the surrounding muscular tissues were completely preserved, and the end-to-end sutures and the mucosa of the soft palate on both sides were aligned. The PSG of all patients was reviewed 6 months after surgery, and the efficacy was classified into three levels according to the degree of AHI reduction with reference to the criteria of Nishimura et al. Significant: AHI reduction of 75% or less than 10; effective: AHI reduction of 74% to 25%; ineffective: AHI reduction of less than 25%. 2. Results (1) Subjective efficacy: 81.25% (52 cases) of the patients’ symptoms such as snoring, breath-holding, drowsiness and headache improved significantly or disappeared after surgery. (2) Objective efficacy: PSG was rechecked 6 months after surgery, 21 cases (32.81%) were significantly effective, 24 cases (37.5%) were effective, and the total effective rate was 70.31%, 19 cases (29.69%) were ineffective. There was no postoperative bleeding, laryngeal edema, dyspnea and palatopharyngeal closure. There were two cases with foreign body sensation and discomfort in the pharynx within two months. The length of the postoperative uvula was basically retracted to the preoperative level in all patients at 2-3 months. Compared with the traditional UPPP, the modified UPPP surgery is characterized by dissecting the palatal sail gap, expanding the soft palate resection area, completely preserving the uvula and the muscle tissue in the soft palate, and maximally preserving the basic structure and physiological function of the pharyngeal cavity [1], relying on the postoperative contraction of the uvula, palatal sail tensor, palatal sail levator and scar tissue of the soft palate on both sides to gradually retract the uvula to the normal physiological level. This not only effectively expands the cross-sectional area of the pharyngeal cavity and improves the efficacy of UPPP surgery, but also avoids the occurrence of some postoperative comorbidities such as palatopharyngeal closure insufficiency. The highest point of soft palate resection is generally decided according to the severity of the patient’s disease, the degree of narrowing of the pharyngeal cavity and the length of the soft palate, and if the PSG index is heavy, the pharyngeal cavity is narrower or the soft palate is longer, the highest point of resection is correspondingly higher and vice versa. Since the anatomy of the upper airway and the severity of the disease vary among patients, UPPP surgery should not mechanically determine the height of soft palate resection, but should vary from person to person to maximize the pharyngeal cavity while preserving the physiological function of the pharyngeal cavity as much as possible. UPPP is currently one of the most effective surgical methods for the treatment of OSAS, but because the pathogenesis of OSAS is not well defined, patients have different sites of upper airway obstruction, different anatomical characteristics, and large individual differences, indiscriminate implementation of UPPP in all patients often results in poor postoperative outcomes. According to the statistics of our department, moderate patients account for about 60-70% of OSAS patients. These patients are generally between 30-50 years old, fat, with tonsillar enlargement of degree II-III, flaccid soft palate but good muscle tone, generally without or with mild cardiovascular disease, with significant postoperative widening of pharyngeal cavity, significant improvement of obstructive symptoms, preoperative combined systemic diseases such as hypertension and The symptoms of systemic diseases such as hypertension and drowsiness, headache, memory loss, etc. before surgery improved or disappeared. In addition, obesity is one of the important causes of OSAS. Obese patients generally have more fat accumulation in the neck, enlarged tongue, and fat accumulation in the soft palate, uvula, lateral wall of the pharynx and hypopharynx, resulting in narrowing of the pharyngeal cavity. For overly obese patients, they are often combined with cardiovascular and endocrine diseases. If surgery is performed blindly, intraoperative and postoperative complications are likely to occur, so surgery should be performed after moderate weight loss.