Objective： To investigate the value of PAPP-A（pregnancy assouated plasma protein-A） in the diagnosis and prognosis of gestational trophoblastic disease （GTD）. Methods： The serum β-HCG（β-human chorionic gonadotropin） and PAPP-A levels of 25 normal pregnant women， 28 patients with complete hydatidiform mole and 38 patients with invasive mole were measured by enzyme linked immunosorbent assay （ELISA） during the periods of diagnosis， treatment and follow-up. Results： Compared with control group， patients with complete mole and invasive mole had higher levels of β-HCG （P ＜ 0.01）. But there was no significant difference between the complete and invasive mole group（P ＞ 0.05）. The PAPP-A level of complete mole group was significantly higher than that of control group（P ＜ 0.01）. The PAPP-A level of invasive mole group was significantly higher than that of complete mole group and control group（P ＜ 0.05）. In complete mole group， serum β-HCG and PAPP-A levels of the patients with malignant sequelae were significantly higher than those with benign sequelae （P ＜ 0.05）. The β-HCG level had no relationship with the clinical stage of invasive mole. However， the PAPP-A level increased with clinical advancement of invasive mole. The levels of β-HCG and PAPP-A gradually decreased after evacuation in patients with complete moles， but maintained positive or even increased in patients with subsequent malignancy. Conclusion： The PAPP-A level can give us some help not only in early diagnosis of hydatidiform mole and invasive mole， but also in the prognosis of malignant sequelae.