CA125 is also known as glycan antigen 125, and a normal CA125 is not enough to completely rule out endometriosis. CA125 belongs to a kind of tumor marker, patients with ovarian epithelial cancer, fallopian tube cancer, endometrial cancer, lung adenocarcinoma, gastrointestinal tract adenocarcinoma and other diseases can see the elevation of this indicator after examination. Most patients with endometriosis have elevated results of tumor markers such as CA125, however, not all patients with endometriosis have elevated CA125, some patients have normal CA125, and endometriosis endometriotic cells do not always secrete CA125. Elevated CA125 has a low sensitivity and specificity for diagnosing endometriosis and cannot be used as an independent diagnostic criterion, and a normal CA125 cannot completely exclude endometriosis.