How to judge the recurrence of cancer can be started from the following aspects.1. Combined with imaging examination, such as CT, MRI or PET-CT examination, if the lesion is found to be more than 50% larger than before, it can be initially judged as recurrence.2. Combined with the examination of tumor marker, such as alpha-fetoprotein for the judgement of primary liver cancer, CEA for the judgement of colorectal cancer and C125 for the judgement of ovarian cancer recurrence, all of them are of certain value. The judgment of recurrence of ovarian cancer by combining with tumor markers, such as AFP for primary liver cancer, CEA for colorectal cancer, and C125 for ovarian cancer recurrence. To diagnose whether it is recurrence or not, we have to rely on the pathology of tumor puncture or the pathology after surgical resection, and we can judge whether it is recurrence or not when cancer cells are detected under the microscope; if cancer cells are found, it can be clearly determined that it is recurrence, and the possibility of recurrence does not exist if no cancer cells are found. In conclusion, the judgment of recurrence should be combined with clinical manifestations, imaging examination and pathological examination results.