The cell-free plasma DNA of the 132 critically ill patients admitted to the emergency intensive care unit ( EICU) was measured by real-time quantitative polymerase chain reaction assay for the humanβ-globin gene. Ac-cording to the prognosis, the patients were divided into survival group (95 cases) and death group (37 cases). Blood samples were collected after EICU admission, 24 hours after admission, 48 hours after admission, and 1 week after admission. 30 age-mached controls were collected from healthy volunteers healthy care centre. Com-pared with control group, at each time point, cell-free plasma DNA concentration was significantly higher in EICU patients (P<0. 05). Cell-free plasma DNA concentrations were higher in hospital non-survivors than in survivors, of which plasma DNA concentration of 24 hours after admission and 48 hours after admission was statistically signifi-cant ( P<0 . 05 ) . The area under the ROC curves ( AUC ) for plasma DNA was bigger than the lactate and A-PACHE IIscore, the maximum of AUC was 0. 847(95% CI 0.648~1.000) at the point of 48 hours after admis-sion.