Objective To determine the median effective dose (ED₅₀) of remimazolam to prevent etomidate-induced myoclonus in elderly male and female patients. Methods A total of 43 elderly patients who underwent general anesthesia surgery in our hospital from January 2022 to June 2022 were recruited in this study. There were 21 cases assigned in the male group and 22 cases in the female group. The dose of remimazolam was determined through sequential administration, with an interval of 0.05 mg/kg. Remimazolam was given intravenously at a dose of 0.2 mg/kg for the first time, and etomidate was given at 3 mg/kg in 1.5 min later, followed by 0.2 μg/kg sufentanil and 0.4 mg/kg rocuronium after disappearance of patient′s consciousness. Then laryngeal mask was placed after induction. Mean arterial pressure (MAP), heart rate and pulse oxygen saturation of patients in the two groups were recorded before induction of etomidate anesthesia (T0), immediately after intravenous infusion (T1), 1 min after intravenous infusion (T2) and 3 min after intravenous infusion (T3). The occurrence of adverse reactions such as nausea, vomiting and aspiration was recorded. SPSS statistics 28.0 was used to process the data. Based on data type, independent sample t-test or rank sum test was adopted for inter-group comparison. ED₅₀, 95% effective dose (ED₉₅) and corresponding 95% confidence interval (CI) were calculated with Probit model to establish a linear regression equation. Then GraphPad software was adopted to draw a dose-effect relationship diagram. Results The ED₅₀ of remimazolam in prevention of myoclonus induced by etomidate was 0.12 (95%CI 0.067-0.169) and 0.17 mg/kg (95%CI 0.127-0.215) respectively for the elderly male and female patients, and the ED₉₅ was 0.19 (95%CI 0.153-0.665) and 0.24 mg/kg (95%CI 0.202-0.580), respectively. In the male group, MAP at T3 was decreased significantly than that at T0 (87.10±6.53 vs 99.99±7.84 mmHg; P<0.05). In the female group, both MAP [(85.50±7.03) vs (102.95±4.03) mmHg] and heart rate [(69.6±5.41) vs (76.00±6.65) beats/min] were obviously reduced at T3 than T0 (P<0.05). However, the decline was not larger than 20% of the base value at T0 before anesthesia. No adverse reactions such as nausea, vomiting and aspiration occurred at T1, T2 and T3. Conclusion The ED₅₀ of remimazolam for preventing etometon-induced myoclonus is 0.12 and 0.17 mg/kg respectively in elderly male and female patients during induction of general anesthesia, and the dose is lower in eldly male than in elderly female. The hemodynamics is stable and no adverse reactions occur during induction.