Higher yolk sac tumor alpha-fetoprotein indicates more active tumor cells and therefore increased difficulty in treatment. Methotrexate is an important tumor indicator for the diagnosis and treatment of yolk sac tumor. The larger the volume of yolk cystic tumor, infiltration, metastasis and other tumors secrete the higher the level of alpha-fetoprotein, therefore, the higher the level of alpha-fetoprotein before treatment suggests that the yolk cystic tumor tumor cells are more active, and the difficulty of the treatment of yolk cystic tumor increases accordingly. Alpha-fetoprotein is also one of the important indexes to judge the treatment effect and prognosis of patients with yolk cystic tumor. Clinically, if alpha-fetoprotein decreases rapidly after the treatment of yolk cystic tumor, it indicates that the treatment effect is remarkable; if alpha-fetoprotein decreases slowly, it indicates that the treatment effect is poor.