Objective:To study the half effective dose of propofol inhibiting pharyngeal response of elderly patients to inserted gastroscope under anesthesia by Dixon sequential method.Methods:In this prospective study, 31 elderly patients aged 75 to 84 years who planned to undergo painless gastroscopy at the Digestive Endoscopy Center of Beijing Friendship Hospital, Capital Medical University from March to June 2021 were enrolled, American Society of Anesthesiologists class Ⅰ-Ⅱ. The heart rate (HR), mean arterial pressure (MAP), peripheral pulse oxygen saturation (SpO 2) were monitored. The propofol dose started at 1.1 mg/kg (the first patient), and the gap dose was 0.1 mg/kg. The sequential dose given to the patient increased by 0.1 mg/kg if the pharyngeal response to inserted gastroscope of the previous patient was not considered inhibited or decreased by 0.1 mg/kg if the pharyngeal response was inhibited, the positive pharyngeal response-inhibited pharyngeal response was regarded as one crossover, and this study stopped after the seventh crossover. The change of MAP, HR and SpO 2 prior to anesthesia, insertion of gastroscope, 2 minutes after insertion, after gastroscopy was recorded. Nausea and vomiting, cough and swallowing, and body movement were also recorded. The measurement data were expressed as mean ± standard deviation ( ± s), and the changes at different time points were compared by repeated measurement data ANOVA. Results:The half effective dose of propofol inhibiting pharyngeal response to inserted gastroscope was (1.11±0.16) mg/kg. The MAP prior to anesthesia, insertion of gastroscope, 2 minutes after insertion, after gastroscopy were (105.05±13.39) mmHg, (90.48±10.98) mmHg, (90.48±11.11) mmHg, (82.68±9.98) mmHg, respectively, and the MAP at each observation point after administration was significantly lower than that before anesthesia, the differences were statistically significant ( P<0.05). The HR prior to anesthesia, insertion of gastroscope, 2 minutes after insertion, after gastroscopy were 77.26±12.67, 72.81±10.39, 72.90±11.63, 68.32±9.42, respectively, and the HR at each observation point after administration was significantly lower than that before sedation, the differences were statistically significant ( P<0.05). The SpO 2 prior to anesthesia, insertion of gastroscope, 2 minutes after insertion, after gastroscopy were (96.48±1.81)%, (98.65±1.31)%, (97.36±2.14)%, (96.48±1.81)%, respectively, and the SpO 2 prior to anesthesia was statistically significant compared with insertion of gastroscope ( P<0.001), the SpO 2 of 2 minutes after insertion, and after gastroscopy were significant differences compared with insertion of gastroscope ( P<0.05). Conclusion:Half effective dose of propofol for inhibiting pharyngeal response to inserted gastroscope under anesthesia by Dixon sequential method was determined as (1.11±0.16)mg/kg .