OBJECTIVE： To investigate the clinical effects of pidotimod in the bronchial asthma complicated with recurrent respiratory tract infection， and its effects on immunoglobulin and related indexes. METHODS： A total of 120 bronchial asthma patients with recurrent respiratory tract infection selected from our hospital during Mar. 2011-May 2013 were divided into trial group and control group according to random number table， with 60 cases in each group. Control group received routine corticosteroid therapy， and trial group was additionally given Pidotimod oral solution 0.4 g， po， bid， for 14 d， on the basis of control group.  Clinical indexes （the times of respiratory infection， the duration of fever， cough， wheezing attack and antibiotics use）， serum indexes [β-defensin-1 （hBD-1）， immunoglobulin A （IgA）， IgG， IgM， UREA， ALT]， the results of pharynx test before and after treatment， and the occurrence of ADR were observed in 2 groups. RESULTS： Before treatment， there was no statistical significance in clinical indexes， serum indexes， the results of pharynx test between 2 groups （P＞0.05）. After treatment， clinical indexes of trial group were significantly lower or shorter then before treatment or control group， while serum levels of hBD-1， IgA and IgG were significantly higher than before treatment or control group， with statistical significance （P＜0.05）. There was no statistical significance in clinical indexes and serum indexes of control group， serum levels of IgM， UREA and ALT in trial group before and after treatment （P＞0.05）. The types and number of pathogenic bacteria of respiratory tract infection were decreased significantly in 2 groups， and the trial group was significantly less then the control group， with statistical significance （P＜0.05）. No obvious ADR was found in 2 groups. CONCLUSIONS： Pidotimod shows good clinical effects on bronchial asthma complicated with recurrent respiratory tract infection， can improve immunity and reduce the types and number of pathogenic bacteria with good safety.