Radiation-induced mucositis is an acute reaction of the mucosa of patients undergoing head and neck radiotherapy.It can lead to dose-limiting and debilitating side effect. There is no guideline on an acknowledged intervention that significantly reduces its severity. In the mucosa, the immune system's T cells and B cells have position-specific phenotypes and functions that are influenced by the microbiota. These cells play pivotal parts in the maintenance of immune homeostasis by suppressing responses to harmless antigens and by enforcing the integrity of the barrier functions of the gut mucosa.We designed a randomized trial of Live Combined Bifidobacterium,Lactobacillus and Enterococcus Capsules in patients with Nasopharyngeal Carcinoma. The aim of this study was to determine if regulating intestinal tract flora was effective in reducing the severity of radiation-induced mucositis in patients receiving radical dose radiotherapy. The effect of this intervention on a patient's general well-being was also investigated. The primary end-point of the study was the incidence of Radiation Therapy Oncology Group grade 3 mucositis.In 2017, 40 patients are estimated to be recruited into the study at Jiangxi Cancer Hospitals, China.20 patients were randomized to receive Live Combined Bifidobacterium,Lactobacillus and Enterococcus Capsules and 20 to receive a placebo.