The aim of this study is to investigate the immune regulation function of scavenger receptor class A type I (SR-AI) on macrophages for the treatment of two common pathogens of respiratory tract: Klebsiella pneumoniae (K. pneumoniae) and Pseudomonas aeruginosa (P. aeruginosa). The clinical isolates of K. pneumoniae and P. aeruginosa were collected. They were stained by fluorescent dyes and subjected to the peritoneal macrophages prepared from wide-type (WT) and SR-AI^－/－ mice respectively. The results showed that SR-AI^－/－ macrophages had lower phagocytic ability to K. pneumoniae, but higher phagocytic ability to P. aeruginosa than WT macrophages. Quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) was used to detect mRNA expressions of inflammatory cytokines. The results showed that the inflammatory reactions of SR-AI^－/－ macrophages were significantly improved than WT macrophages after infection of K. pneumoniae and P. aeruginosa. The data suggest that SR-AI could participate in the phagocytosis of K. pneumoniae by macrophages, but not in the phagocytosis of P. aeruginosa. Besides, SR-AI plays a role in downregulation of inflammatory reactions induced by infection of K. pneumoniae and P. aeruginosa.