Objective To observe the expression of S100A8 and S100A9 in alveolar macrophages (AMs) of chronic obstructive pulmonary disease (COPD) rats, and explore the effect on the release of inflammatory mediators from AMs in COPD rats. Methods Twelve adult male Wistar rats were randomly divided into a normal control group and a COPD group. The COPD model was established by exposing the rats to cigarette smoke and intratracheal injection of endotoxin for 1 month. The pathological changes of lung tissue of rats were observed under light microscope. Total cells counts and the number of AMs, lymphocytes, neutrophils in bronchoalveolar lavage fluid (BALF) of two groups were examined by Wright's staining methods. Rat AMs from the control group and the COPD group were isolated and cultured, and then treated with different doses of S100A8 and S100A9 for 6 hours and 12 hours. The levels of interleukin (IL)-8, IL-6 and tumour necrosis factor-α (TNF-α) in the AMs supernatants were measured by enzyme linked immunosorbent assay. The expression of S100A8 and S100A9 mRNA in AMs of rats were observed by in situ hybridization. The immunohistochemical method was used to observed the expression of S100A8/A9 protein of AMs. Results After cigarette smoking combined with intratracheal injection of endotoxin for 1 month, the lung tissue of rats showed typical pathological changes of COPD. Total cell counts and the number of AMs, lymphocytes, neutrophils in BALF of the COPD rats were significantly higher than those of the normal rats (P<0.05). Among them, the increase in the number of AMs was the most obvious. Compared with the control group, the expression of S100A8 mRNA, S100A9 mRNA and S100A8/A9 protein in AMs of the COPD group were up-regulated significantly (P<0.05). After the AMs of COPD rats were treated with S100A8 and S100A9, the contents of IL-8, IL-6 and TNF-α in AMs supernatants increased significantly in a time- and dose-dependent manner. When the AMs were treated with the same dose of S100A8 and S100A9 for the same time, the levels of IL-8, IL-6 and TNF-α in the AMs supernatant of the COPD group were higher than those of the normal control group. Conclusions The expression of S100A8 and S100A9 in cultured COPD rat AMs is significantly increased. S100A8 and S100A9 can promote the secretion and release of inflammatory factors IL-6, IL-8 and TNF-α from AMs of COPD rats in a time and dose-dependent manner. The effects of S100A8 and S100A9 on the secretion of IL-6, IL-8 and TNF-α in AM of COPD rats are significantly enhanced compared with those of normal rats.