Abstract: Objective To develop a differential equation kinetic model， and explore the dynamics of plasma Epstein-Barr virus（EBV）-DNA concentration for nasopharyngeal cancer（NPC） patients undergoing radiation therapy. Methods Ten NPC patients treated with intensity modulated radiotherapy from January 2013 to December 2014 were involved in this study. The content of EBV-DNA in the plasma samples were detected by using fluorescent quantitative PCR method. Results Fitting of the model to the data of plasma EBV-DNA levels allowed determination of the different parameters describing the radiosensitivity， dead-cell resolving and necrotic cell fraction. These parameters were correlated with patterns of the dynamics of plasma EBV-DNA level during radiotherapy， and it may be indicative of the clinical phenotype. Conclusion The model parameters may have a potential to predict biological characters of tumor， though further validation in a larger pool of samples is warranted.