Portal vein thrombosis (PT) can occur in any section of the portal vein, and refers to thrombosis in the portal vein trunk, superior mesenteric vein, inferior mesenteric vein or splenic vein. Portal vein thrombosis can cause portal vein obstruction, increase portal vein pressure and intestinal congestion, and is the main disease causing extrahepatic portal hypertension. It is relatively rare in clinical practice. In recent years, with the widespread application of color Doppler and the improvement of diagnostic level, the number of case reports has increased day by day. The cause may be related to systemic or local infection and portal vein congestion. It can also be seen after hepatobiliary surgery and splenectomy. Clinically, more than half of the cases still cannot find the cause. Portal vein thrombosis is divided into primary and secondary. It can be divided into intrahepatic and extrahepatic according to the location, and acute and chronic according to the onset. Clinically, secondary portal vein thrombosis is relatively common, mostly secondary to chronic liver disease and tumor diseases. Extrahepatic portal vein obstruction is mostly secondary to intrahepatic portal hypertension. The main clinical manifestation is abdominal pain, the severity of which depends on the location, rapidity, range and degree of thrombosis. The most prominent symptom of simple extrahepatic portal vein obstruction is esophageal varicose bleeding. Because this disease has no characteristic manifestations, it is easy to misdiagnose clinically.