Objective To investigate the effective dose of remimazolam benzenesulfonate to suppress cardiovascular responses to laryngeal mask placement in elderly patients. Methods Elderly patients undergoing laryngeal mask anesthesia between March and June 2023 were selected. Combined with sulfentanil 0.2 μg/kg, remimazolam was used as induction hypnotic. The first patient was given remizolam benzenesulfonate 0.16 mg/kg infused by pump for 1 min. The dose of remimazolam for the next patient was determined by the biased coin up-and-down method based on the patient’s response to the laryngeal mask placement. The score of Modified Observer’s Assessment of Alert/Sedation, vital signs and anesthesia depth index (AI) were recorded during induction. Probit analysis was used to calculate the half effective dose (ED50), 95% effective dose (ED95) and half effective AI (AI50). According to the statistical requirements, at least 45 negative patients were required. Results A total of 53 elderly patients were enrolled in the study until the end of the trial. The ED50 and ED95 of remimazolam benzenesulfonate for inhibiting cardiovascular responses to laryngeal mask insertion were 0.154 mg/kg [95% confidence interval (CI) (0.034, 0.170) mg/kg] and 0.207 mg/kg [95%CI (0.190, 0.614) mg/kg], respectively. AI decreased during induction, with an AI50 of 64.119 [95%CI (60.609, 69.984)]. Conclusion When combined with 0.2 μg/kg sufentanil, infusing 0.2 mg/kg remimazolam benzenesulfonate for 1 min is effective and safe for laryngeal mask anesthesia induction in elderly patients.