Abstract: This study investigated the relationship between the microsatellite polymorphism in the Heme Oxygenase-1(HO-1)gene promoter and expressive levels of induced nitric oxide synthase(iNOS). The relationship was analyzed by techniques of polymerase chain reaction(PCR) and immunohistochemistry in the lung tissues from 80 cases of the patients with lung cancer ,containing 50 cases of patients with COPD (COPD group) and 30 patients without COPD (control group).The results showed that the stronger positive rate of iNOS expression in COPD group was significant higher than those of the control groups（P ﹤0.01）and that the stronger positive rate of iNOS expression in the subjects with a class L allele of the (GT)n repeats of the HO-1 gene promoter（L/L, L/M and L/S）was statistical higher compared with that of the subjects without a class L allele ( M/M, M/S and S/S)（P ﹤0.01）. This results suggest that there is likely a increase of the expressive levels of iNOS in the subjects of genotypes with ≥ 30 GT repeats in the HO-1 gene promoter region, which may be associated with the susceptibility to COPD.