Objective To investigate the reasons and preventions of bleeding after percutaneous microwave ablation for liver cancer. Methods The data of 156 patients with liver cancer between September 2006 and December 2009 treated with percutaneous microwave ablation (226 times) were recorded. The reasons and preventions of bleeding after percutaneous microwave ablation were analyzed. Results Eleven patients (11 times) suffered from bleeding. The rate of bleeding is 4.87% (11/226), including 2 cases of biliary bleeding, 9 cases of intraperitoneal hemorrhage. All patients who suffered from bleeding firstly received medical therapy to control bleeding, 5 cases were successful; in the other 6 cases who failed in medical therapy, 1 case was stopped bleeding with opening procedures, 4 cases received transcatheter embolization to stop bleeding with gelatin sponge, 1 case died due to excessive blood loss. According to Chi-square test result, the bleeding was significantly related with liver cirrhosis, lower platelet count, obvious prolongation of prothrombin time, subcapsular tumor, Child-Pugh B/C grade, and re-ablation （P=0.044, 0.041, 0.028, 0.001, 0.016, 0.016）. The multiple variables logistic regression analysis showed that liver cirrhosis, platelet count, prothrombin time, location of tumor, and Child-Pugh grade were the influential factors of bleeding after microwave ablation （OR=5.273, P=0.036; OR=8.534, P=0.043; OR=4.893, P=0.045; OR=7.747, P=0.010; OR=6.882, P=0.015）. Conclusions There were some factors were significantly related with the bleeding after percutaneous microwave ablation: liver cirrhosis, abnormal blood clotting function （lower platelet count and prolongation of prothrombin time）, tumor located on the surface of liver, and Child-Pugh C grade. When failed to stop bleeding with medical therapy, transcatheter embolization is an effective method to control bleeding.