Background: Obstructive sleep apnea (OSA) refers to the apnea and hypopnea caused by upper airway obstruction during sleep. Patients are associated with sleep disorders, frequent desaturation, hypertension, coronary heart disease, cerebrovascular disease and diabetes. OSA prevalence increased in China in recent years. It is estimated that nearly 80% of men and 93% of women are not diagnosed for moderate and severe OSA. Anesthesiologists and surgeons paid more attention on those high risk patients. The gold standard for OSA diagnosis is apnea and hypopnea index (AHI) obtained from polysomnography (PSG). But it is difficult to carry out PSG regularly in primary health care institutions in China for its high cost and long waiting list. So many OSA questionnaires are developed in Europe and North America, obesity is an important risk factor for OSA for them. But in China people have different anatomical characteristics, the diagnosis sensitivity and specificity of those methods has not been reported in China. Methods and Design: Participants for this study will be recruited in Beijing Tongren Hospital scheduled for elective surgery under general anesthesia. A total of 1200 adult male patients will be enrolled. It is including 3 kinds of persons. 1. To accept PSG monitor in sleep center. 2. To receive OSA correction surgery (UPPP). 3. To receive ophthalmological surgery under general anesthesia. Detailed inquiry and record all medical history. Upper airway assessment will be recorded. Preoperative snoring questionnaires will be integrated according to the four questionnaires. All patients complete PSG monitor. For patients undergoing surgical treatment, postoperative continuous pulse oximetry will be recorded for 24 hours. All postoperative adverse events will be recorded. The primary endpoint: All the patients complete the four snoring questionnaires (ASA, Berlin, STOP and STOP-BANG) before PSG test. The secondary endpoints: PSG monitor will be completed before operation. Medical history, upper airway assessment, postoperative 24 hours continuous pulse oximetry monitor and all perioperative adverse events will be recorded. The purpose is to compare the specificity and sensitivity of four questionnaires to figure out OSA. To find suspected OSA patients before operation with one easy-to-use assessment questionnaire and direct OSA clinical practice.