Abstract: Objective To explore the clinical significance of plasma epstein-barr virus DNA（EBV-DNA） quantitative monitoring in the treatment and follow-up for locally advanced nasopharyngeal carcinoma. Methods Plasma EBV-DNA levels of 156 locally advanced nasopharyngeal cancer patients were detected during concurrent radiochemotherapy with 0， 2， 4， 6， 8 weeks， and plasma EBV-DNA levels of patients with who plasma EBV-DNApositive before the treatment and followed up were detected after 6， 12， 18， 24 months， using quantitative PCR technique. The efficacy and recurrence and metastasis situation during two years after treatment were evaluated respectively. Results Plasma EBV-DNApositive rate of 156 patients was 91.0％ （142／156） before concurrent radiochemotherapy， and positive rate of 9.6％ （15／156） after 8 weeks of the treatment. One hundred and twenty-seven out of 142 plasma EBV-DNApositive patients with pretreatment， plasma EBVDNA levels showed a trend of decline from the treatment of 2 weeks. On 6 weeks of the treatment， DNA replication were not detected in 127 patients. The other plasma EBV-DNA level of 15 cases maintained the positive level after 8 weeks of the treatment. One hundred and nineteen cases were complete response and 37 cases were partial response， of which the plasma EBVDNA positive rate of 8 weeks after the treatment was 3.4％ （4／119） and 29.7％ （11／37）， respectively. 135 out of 142 patients with pre-treatment plasma EBV-DNApositive were followed up for two years， 1， 2year recurrence rate was 14.1％ （19／135） and 23.0％ （31／135）， respectively. By receiver operating characteristic curve analysis， 1， 2year plasma EBVDNA levels were higher judged on accuracy of 1， 2year recurrence rate （Az1=0.944，Az2=0.925；P＜0.05）. Conclusion Quantification of plasma EBV-DNA level can better reflect the efficacy of locally advanced nasopharyngeal carcinoma after comprehensive treatment. For pretreatment plasma EBV-DNApositive locally advanced nasopharyngeal carcinoma， there is a good clinical value to determine recurrence and metastasis by realtime monitoring of plasma EBVDNA level during two years after concurrent radiochemotherapy.