Objective To compare the effects of morphine and butorphanol on the intra-abdominal pressure (IAP) in the patients following gastrointestinal surgery. Methods Eighty patients who were admitted to our Intensive Care Unit after gastrointestinal open surgery from November 2016 to September 2017 were prospectively enrolled in this study. They were randomly divided into morphine group (n=40) and butorphanol group (n=40). After operation, the patients from the former group were injected with 20 mg morphine plus normal saline (totally 40 ml) for analgesia, and those from the latter were given 4 mg butorphanol plus normal saline (totally 40 ml), both at a speed of 2 ml/h, for over 24 h. The clinical indices and IAP level at different time points were compared between the 2 groups. SPSS statistics 21.0 was used for statistical analysis, and Student′s t test or Chi-square test was adopted for comparison between groups depending on the types of data. Results The IAP level in the butorphanol group was significantly lower than that in the morphine group at 24 h [(13.38±2.03) vs (14.76±3.05)mmHg, 1 mmHg=0.133 kPa] and 48 h [(12.33±1.75) vs (14.04±2.70)mmHg] after treatment (P<0.05). The patients of the butorphanol group had shorter recovery time of gastrointestinal function [(2.65±0.66) vs (3.05±0.67)d] and length of postoperative hospital stay [(10.08±1.64) vs (12.00±2.56) d], and lower incidence rates of postoperative nausea and vomiting (10.00% vs 27.50%), but higher rate of drowsiness (25.00% vs 7.50%) when compared with those from the morphine group (all P<0.05). Conclusion As analgesic drug, butorphanol may be more suitable than morphine for the patients after gastrointestinal open surgery.