Objective　To study the alterations of surfactant protein A (SP-A) and B (SP-B) in rats in the early stage of acute lung injury induced by oleic acid. Methods　An acute lung injury model was established by injecting oleic acid into the superior vena cava of rats and the levels of SP-A and SP-B in branchoalveolar lavage fluid (BALF) were determined with Western Blot and ELISA. Results　The levels of SP-A and SP-B in BALF were significantly decreased in the injured group 1 h after acute lung injury (P<0.01) and remained low in the next 6 h. Conclusion　The levels of SP-A and SP-B were decreased in the early stage of acute lung injury. The methods used for detecting SP-A and SP-B we adopted are specific and sensitive, and might be helpful for other experimental study.