Abstract: Objective: To explore the value of the intraperitoneal free gas distribution of multislice CT(MSCT) in the positioning diagnosis of upper and lower gastrointestinal perforation.Methods: The distribution characteristics of intraperitoneal free gas in MSCT of 54 patients with gastrointestinal perforation were retrospectively analyzed,which was compared with surgical results.Results: The distribution proportions of MSCT intraperitoneal free gas in hepatic portal,falciform ligament,ligamentum teres hepatis and stomach and duodenum of the patients with upper gastrointestinal perforation were significantly higher than those of the patients with lower gastrointestinal perforation(P<0.05 to P<0.01).The distribution proportions of MSCT intraperitoneal free gas in jejunum and ileum,mesentery,appendix and pelvic cavity of the patients with upper gastrointestinal perforation were significantly lower than those of the patients with lower gastrointestinal perforation(P<0.05 to P<0.01).Conclusions: The distribution of the free gas in MSCT is conducive to identify the upper and lower gastrointestinal perforation,and can improve the diagnostic accuracy before operation.