To observe the effect of radiotherapy (RT) combined with ginseng polysaccharide (GSP) injection in treating nasopharyngeal carcinoma (NPC) and its influence on immune function.Methods: One hundred and thirty-one patients of NPC were randomly divided into two groups, the RT-GSP group (n=64) treated with RT and GSP, and the control group (n=67) treated with conventional radiotherapy, to observe the local cancer remission rate, 1-year total survival rate, no tumor survival rate and no remote metastasis survival rate. Moreover, the changes of T-lymphocyte subsets, natural killer cell (NK) activity and lymphokine-activated killer cell (LAK) activity before and after treatment were determined.Results: Clinical examination conducted 3 months after treatment showed that the complete remission rate in the RT-GSP group was 96.6%, and in the control group 93.3%, the complete remission rate of cervical lymph node metastasis in the two groups was 85.7% and 78.0%, the NPC remission rate shown by CT 60.3% and 51.7%, respectively. Re-examination carried out 1 year after treatment showed that the total survival rate in the two groups was 100% and 96.5%, tumor free survival rate 84.4% and 74.6%, and no remote metastasis survival rate 93.8% and 88.1% respectively. The activity of NK cell and LAK cell as well as T3, T4 value in peripheral blood increased significantly in the RT-GSP group (all P<0.05) after treatment, while with the control group, no significant influence on NK and LAK activities were shown but significant lowering of T3, T4 was, P<0.05. No toxic-adverse reaction of GSP was found.Conclusion: GSP has certain immune function improving effect in NPC patients during RT, and it could also eliminate the occurred adverse reaction to RT and improve the general condition of patients.