This kit is used for quantitative detection of tumor associated antigen CA125 in human serum in vitro. Tumor associated antigen CA125 is a kind of glycoprotein tumor marker with molecular weight of 200-1000kda, which is related to epithelial ovarian cancer and other tumors. It is expressed on the epithelial cell membrane of the cancerous ovary and can be released into the intercellular substance and patient serum. It is an epithelial ovarian cancer-related antigen, which is an indicator of diagnosis, staging, prognosis and efficacy monitoring of epithelial ovarian cancer. The level of CA125 in patients with other malignant tumors can also be significantly increased, while the level of CA125 in non malignant tumor diseases such as female pelvic inflammation, endometriosis, endometritis, hysteromyoma, cervicitis, pregnancy, chronic hepatitis, acute and chronic pancreatitis, renal failure and autoimmune diseases can be slightly increased. This kit is used to assist diagnosis, efficacy evaluation and dynamic monitoring of disease progress in patients with serous ovarian cancer.