This study was aimed to quantify plasma circulating DNA level in patients with acute myeloid leukemia (AML) and to evaluate its clinical significance. 66 AML patients and 100 controls (60 healthy subjects for health examination, 20 cases of benign hematopathy, and 20 cases of solid tumors) were enrolled in this study. Blood samples were collected from AML patients at different status of disease and control groups. Circulating DNA were drew by using the BILATEST DNA Kit. The level of plasma DNA was determined by using duplex real-time quantitative PCR. The results showed that the median value of plasma DNA level in AML patients at diagnosis was 168.5 (73.4 - 245.1) ng/ml, significantly higher than those in three control groups, and the median level in male patients was significantly higher than that in female patients (P = 0.019). No significant difference was found in plasma DNA level of the patients at different ages and with different FAB subtypes. Compared with level before chemotherapy, the plasma DNA levels in complete remission patients and partial remission patients decreased significantly, and with no statistical difference from level of healthy controls, but was significantly different from level of non-remission patients (P < 0.05). Following up of 31 remission patients showed that the plasma DNA level increased in 5 out of 6 (83.3%) relapsed patients, but no increase was found in 22 out of 25 (88.0%) non-relapsed patients. It is concluded that the quantification of plasma DNA may be useful for evaluating therapeutic effects and monitoring relapse in AML patients.