Objective：To investigate the current situation and therapeutic strategies for obstetric patients in ICU with invasive me－chanical ventilation（IMV）. Methods：Totally 44 patients in obstetric ICU using only IMV were enrolled，24 patients were survived and 20 patients were died. Patients’ blood gas，respiratory rate，PO2，PO2/FiO2 before entering ICU and at 1 h，8 h，24 h and 48 h after IMV were observed and compared. Acute physiology and chronic health evaluationⅡ（APACHEⅡ） and therapeutic intervention scor－ing system（TISS） were used to assess disease severity and estimated the risk of death for these patients. Results：APACHEⅡ score，mortality risk factor，TISS score，PO2/FiO2，number of pregnancies were different（statistically significant，P<0.05） between survival group and death group.The differences of postpartum hemorrhage，anemia，DIC，shock，MODS，hypertensive disorder complicating pregnancy were statistically significant（P<0.05） between the two groups. SPO2 and respiratory rate were stabilized with 1 h IMV.PO2/FiO2 was improved significantly after 8 h IMV，but internal environment was not significant improved.Patients’pH，PCO2，BE，FiO2 were significantly different with 48 h IMV（P<0.005）. Conclusion：Obstetric patients in the ICU with invasive mechanical ventila－tion have higher mortality rate if they are withdrawn in a short period. APACHEⅡand TISS are valid evaluations for assessing disease severity. Internal environment is not significant improved after 8 h of IMV and hastily reducing ventilator parameters is not desirable. IMV for 8-24 h might be suitable for estimating prognosis；24 h is a preferable observation point than others. Risk of death is higher when IMV>24 ht；it is even worse at 48 h. Deterioration of in－ternal environment such as acid-base imbalance may be the main factors that accounted for patients’ morbidity and should be the focus of treatment.