This study is to investigate the pharmacological effect and mechanism of action of hydroxysafflor yellow A (HSYA) on acute lung injury (ALI).  The rat ALI was induced by oleic acid and lipopolysaccharide (LPS) injection.  The incidence of acidosis, PaO₂ (arterial blood oxygen pressure), W/D (wet weight/dry weight) and lung index (LI) were measured.  Electron microscope and optical microscope were applied to observe lung morphological changes in rat.  RT-PCR was used to determine TNF-α and ICAM-1 mRNA level.  Inhibition effect of HSYA on plasma inflammatory cytokine expression was measured by ELISA.  HSYA could alleviate pulmonary edema, reduce acidosis, keep PaO₂ from descending, inhibit inflammatory cell infiltration, inhibit rat lung TNF-α and ICAM-1 mRNA expression and plasma IL-6 and IL-1β level elevation.  HSYA is an effective ingredient to remit ALI induced by oleic acid and LPS in rat.