The patient, a 50-year-old woman, was admitted to hospital diagnosed with gastric cancer. While performing preoperative examination, we found that this patient had a lack of factor XI. This is the first case diagnosed with gastric cancer combined with lack of emitted factor XI, at least in China. We used only fresh frozen plasma to correct the blood coagulation disorder to perform an operation. Firstly, we think this is a rare case that should be reported. Secondly, what we have done to help this patient may help other doctors to make decisions when they meet any similar cases.