Objective: To explore the effect of different doses of pentazocine in painless gastroscopy. Methods: A total of 200 patients who underwent painless gastroscopy in the First Affiliated Hospital of Hebei North University from January 2022~January 2023 were selected. All patients were divided into four groups: group A (pentazocin 0.2 mg·kg-1), group B (pentazocine 0.5 mg·kg-1), group C (pentazocine 0.8 mg·kg-1) and group D (control group: sufentanil 0.08 ug·kg-1), with 50 cases in each group. Observation indicators: The behavioural pain scale non-infused (BPS-NI) score was used to compare the analgesic effect of the four groups. The mean arterial pressure (MAP) pressure and heart rate (HR) of the four groups were compared before operation (T0), gastroscopy across the glottis to the upper esophageal end (T1), and at the time of awakening (T2), and the recovery time, recovery ventricular retention time and total amount of propofol were recorded. The occurrence of intraoperative and postoperative adverse reactions was compared. Results: Compared with group D (control group), group A had worse analgesic effect (P<0.05), and the dosage, recovery time and retention time of PACU were higher than those in group D. The dosage of propofol in group C was lower than that in group D, but the recovery time and retention time and incidence of adverse reactions in group C were significantly higher than those in group C (P>0.05). The BPS-NI score and analgesic success rate of group B were similar to those of group D (P>0.05), but the incidence of postoperative adverse reactions was lower than that of group D, and the hemodynamic stability was better than that of group D. Conclusion: Pentazocine at 0.5 mg·kg-1 has the best effect in painless gastrointestinal endoscopy, which is worthy of clinical promotion.