Objective To explore the clinical curative effect of pidotimod on patients with respiratory tract infection and effect on immune function. Methods 120 children with recurrent respiratory tract infection in the Third Hospital of Qinhuangdao,the Third Staff Hospital of Baogang Group,the Third Hospital of Wulanchabu were selected,and were divided into two groups according to random number table.60 cases in control group were treated with routine treatment of anti-infection,relieving cough,eliminating phlegm,antipyretic;60 cases in experimental group were treated with pidotimod on the basis of routine treatment,oral with boiled water,0.4g per times,2 times a day,with a course of 60 days.Clinical curative effect after treatment and serum immunoglobulin (IgG,IgA,IgM)levels,T lymphocyte subsets (CD3+,CD4+,CD8+)levels and NK cells relative activities before and after treatment were compared between two groups.Results After treatment,the total effective rate of experimental group (95.00%)was significantly higher than that of control group (81.67%),and the difference was statistically significant (P<0.05);the immune indexes before treatment had no significant difference,and levels of serum immunoglobulin and T lymphocyte subsets were improved,and levels of serum immunoglobulin (IgG,IgA,IgM)and T lymphocyte subsets (CD3+,CD4+,CD8+)of experimental group were more higher than those of control group,and the difference was statistically significant (P<0.05 );relative activity of NK cells in both groups improved after treatment,but relative activity of NK cells in experimental group was significantly higher than that in control group,and the difference was statistically significant (P<0.05 );adverse reactions according minor rashes and anemia were observed in two groups,and there was no significant differece in the incidence of adverse reactions,and ADR was tolerable after symptomatic treatment.Conclusion Pidotimod could significantly improve the clinical curative effect of patients with respiratory tract infections and effectively improve the immune function of patients with recurrent respiratory tract infections with high security,which has a clinical significance.