Objective To study the relationship between viral infection and chronic obstructive pulmonary disease (COPD),and the effect of viral infections on the changes of Th1/Th2 in COPD patients. Methods The se-ra from 81 patients with acute exacerbations of COPD,25 patients with stable COPD and 22 healthy subjects were tested for specific IgM of respiratary syncytial virus(RSV) ,herpes simplex virus type 1 (HSV-1), parainfluenza vi-rus (PIV), adenovirus (ADV) and cytomegalovirus (CMV) by indirect enzyme-linked immunosorbent assay (ELISA). Supernatant INF-γ and IL-4 cultured with PHA were determined. Results The positive rates of IgM in patients with acute exacerbations of COPD compared with those in patients with stable COPD and healthy subjects were significantly different(P <0.001 ). The level of INF-γ, and IL-4 in patients with acute exacerbations of COPD and stable COPD compared with normal control group;the level of INF-γ (242±43) and the of IL-4(42±9) in pa-tients with acute exacerbations of COPD was not significantly different as compared with the level of INF-γ( 198±32) and the level of IL-4(56±11 ) in patients with stable COPD (P<0.05), but the level of INF-γ was increased (90±18)and IL-4 was decreased (141±24) in control group (P<0.05). Compared with those in IgM negative group, the levels of INF-γ were significantly higher and the levels of IL-4 were significantly lowerIL-4 in lgM positive group( P<0.01 ). Conclusion Virus infection is a rather important factor in acute exacerbations of COPD, and COPD is characterized by a predominance of Th1-type response,and there is more significant Th1 response predomi-nance in COPD with virus infection.