Circulating DNA is a potential biomarker for tumor diagnosis and prognosis. This study was aimed to quantify the circulating DNA in plasma from patients with hepatocellular carcinoma (HCC) using quantitative PCR and evaluate its potential clinical value. Blood samples were collected from 72 patients with HCC, 37 with liver cirrhosis or chronic hepatitis and 41 healthy volunteers. Plasma DNA was extracted and quantified by a real-time quantitative PCR method. The diagnostic and prognostic value of plasma DNA analysis for HCC was evaluated. DNA levels in the HCC plasma (median: 173 ng/mL) were significantly higher than those in the healthy controls (9 ng/mL) or control benign patients (46 ng/mL) (P < 0.001). The area under the receiver-operation characteristic (ROC) curve (AUC) assessing plasma DNA was 0.949 for healthy controls and 0.874 for control patients. Plasma DNA detection could discriminate HCC from normal controls with 90.2% sensitivity and 90.3% specificity at the cut-off value of 18.2 ng/mL. Combined ROC analyses using plasma DNA and serum AFP revealed an elevated AUC of 0.974 with 95.1% sensitivity and 94.4% specificity in discriminating HCC from normal controls. The plasma DNA levels were positively associated with tumor size (P = 0.012), and were significantly elevated in HCC patients with intrahepatic spreading or vascular invasion (P = 0.035). The overall survival time of patients with high plasma DNA levels showed a shortened tread when compared with that of patients with low plasma DNA concentrations (P = 0.071). Plasma DNA may be a valuable noninvasive tool for the detecting and predicting the metastasis potential of HCC; and the prognostic value of plasma DNA needed further investigation.