Objective To explore the effect of BCG-polysaccharide nucleic acid(BCG-PSN) on the numbers of Th3,Th2 and Th1 cells in peripheral blood mononuclear cell(PBMC) and airway inflammation status in patients with asthma.Methods Twenty-six patients with moderate persistent asthma were enrolled into the study and randomly divided into simple medication group(n=13,accepted Fluticasone/salmeterol alone) and combined medication group(n=13,accepted Fluticasone/salmeterol+BCG-PSN together).The numbers of Th3,Th1 and Th2 cells in PBMC, the serum levels of TGF-β,IFN-γ,IL-4 and IgE and the clinical effect and airway inflammation status were observed at three time points: before,1.5 months after and 3 months after treatment. Results (1)At 1.5 months after treatment,the Th1/Th2 number was significantly higher in the combined medication group than the simple medication group(1.20±0.57 vs 0.79±0.39,t= 2.129,P＜0.05),and the asthma control test scale(ACT) showed similar difference(18.31±1.75 vs.15.54±2.40,t=3.359,P＜0.01) between the two groups.(2)At 3 months after treatment,the Th1/Th2 number was significantly higher in the combined medication group than the simple medication group(1.73±0.74 vs1.16±0.48,t=2.327,P＜0.05),and the ACT also showed the same kind of difference(22.46±1.13 vs.20.23±2.59,t=2.851,P＜0.01) between the two groups.In addition,at this time point the PEF variability was significant lower in the combined medication group than the simple medication group([9.88±2.18]% vs.[12.05±2.74]%,t=2.235,P＜0.05).(3)We found no significant differences in the comparisons of the numbers of T helper cell subsets in PBMC ,the serum levels of cytokines and IgE,the numbers of inflammatory cells in induced sputum between the two groups(Ps＞0.05).(4)No correlation were found between Th3 cell numbers in PBMC and the serum levels of IgE in the two groups.Conclusion The combined use of Fluticasone/salmeterol and BCG-PSN can further correct the imbalance of Th1/Th2 cells,alleviate clinical symptom of asthma and airway hyper-responsiveness.The therapeutic efficacy improves along with the therapy period,better in the combined medication group than the simple medication group.BCG-PSN has no significant effects on the numbers of Th3 in PBMC in patients with asthma.