Ｏｂｊｅｃｔｉｖｅ　To investigate the effects of dexmedetomidine (Dex) on intestinal barrier function (IBF) after surgery of patients with malignant obstructive jaundice (MOJ).　Methods　Forty patients with MOJ required for operation were selected, and were randomly divided into Dex group (n=20) and control group (n=20). All patients were anesthetized with general anesthesia. Dex group received intravenous infusion of Dex at a dose of 0.5 μg/kg 10 min before induction of anesthesia. In the course of surgery to 0.4 μg·kg-1·h-1 pump injection for 20 min before the completion of surgery. Control group was injected with the same volume of normal saline. Peripheral venous blood was sampled when the patients were in the operating room (T1), at the end of operation (T2), 24 h after operation (T3) and 48 h after operation (T4). The concentration of diamine oxidase (DAO) was measured by enzyme-linked immunosorbent assay (ELISA). Qualitative detection of Escherichia coli DNA was performed by polymerase chain reaction (PCR) technique.　Results　Two groups of plasma DAO levels in patients had no significant differences (P>0.05) at T1. However, control group was significantly higher than Dex group at T2, T3 and T4, and the difference was statistically significant (P<0.05). The Escherichia coli DNA test was negative at T1. From T2 to T4, the positive cases of Escherichia coli DNA was increased (T2