Objective To analyze the clinical characteristics of patients with liver cirrhosis complicated with portal vein thrombosis (PVT) and to explore the high risk factors of PVT formation for the prevention and early treatment of PVT.Methods From January 2012 to August 2017,at the Second Hospital Affiliated to Chongqing Medical University,160 hospitalized liver cirrhosis patients complicated with PVT were selected as PVT group and secondary PVT caused by other factors were excluded.At the same time,250 patients with liver cirrhosis without PVT were enrolled as the control group.According to the history of splenectomy,the patients were divided into splenectomy group and non-splenectomy group.The risk factors correlated with the formation of PVT such as hemoglobin,platelet count,prothrombin time (PT),international normalized ratio (INR) and prothrombin activity were collected.T test,chisquare test and non-parameter rank test were performed for the comparison of above indexes between PVT group and control group.Single factor analysis and multifactor logistic regression were used to analyze the risk factors of PVT formation.Results The average age of patients in PVT group ((54.5 ±11.4) years) was significantly older than that in control group ((51.8±911.9) years,t=2.29,P=0.02).The results of multifactor logistic regression analysis showed that hemoglobin,platelet count,PT and INR were risk factors of PVT formation (all P＜0.05).The proportion of patients with Child-Pugh class C cirrhosis in PVTgroup was higher than that in control group (16.2％,26/160 vs.4.4％,11/250),and the difference was statistically significant (x2 =16.60,P＜0.01).In PVT group,27.5％ (44/160) patients had a history of splenectomy,and 8.4％ (21/250) patients of the control group had a history of splenectomy,and the difference between two groups was statistically significant (x2=26.70,P＜0.01).The platelet counts of patients with splenectomy were higher than those of patients without splenectomy ((176.2±98.7)× 109/L vs.(78.3±57.8) × 109/L),and the difference was statistically significant (t=11.08,P＜0.01).The incidence of complications in PVT group was much higher than that in control group (45.0％,72/160 vs.10.0％,25/250,x2=66.17,P＜0.05).There were no statistically significant differences in the incidence of gastrointestinal bleeding and mortality between PVT treatment group and non-treatment group (25.6％,11/43 vs.23.8％,10/42;18.6％,8/43 vs.31.0％,13/42,respectively;both P＞0.05).Conclusions Decreased hemoglobin,increased platelet count,prolonged PT,increased INR and Child-Pugh classification are the risk factors for PVT formation.Increased platelet after splenectomy is an independent risk factor for PVT formation.