Objective To calculate median effective dose (ED50) and 95% effective dose (ED95) of remimazolam combined with dezocine for gastroscopy in elderly patients. Methods Thirty⁃one patients, 65‒86 years old, weighting 45‒87 kg, undergoing painless gastroscopy were selected in this study in December 2020, American Society of Anesthesiologists (ASA) physical status Ⅰ‒Ⅲ. The vital signs were monitored while remimazolam being administered 10 min after intravenously administering 20 μg/kg dezocine. Gastroscopy was performed after the loss of consciousness in patients. Meanwhile, the anesthetist observed the patient's response to the endoscopic examination. Dixon's up⁃down method was used to estimate the dose of remimazolam. 0.20 mg/kg was set as the initial dose. ED50, ED95 of remimazolam and 95% confidence intervals (CI) were calculated by probabilistic unit (Probit) regression analysis. Results Patients administered remimazolam showed a transient decrease in mean arterial pressure (MAP), heart beat, and pulse oxygen saturation (SpO2) compared with pre⁃medication. ED50 of remimazolam combined with dezocine for gastroscope in elderly patients is 0.184 (0.062‒0.275) mg/kg and ED95 is 0.354 (0.268‒1.677) mg/kg. Conclusions ED50, ED95 of remimazolam combined with dezocine for gastroscopy in elderly patients are 0.184 mg/kg and 0.354 mg/kg respectively.