Background: Salvianolic acid B (Sal B) is a bioactive water-soluble compound of Salviae miltiorrhizae, a traditional herbal medicine that has been used clinically for the treatment of cardiovascular diseases. This study sought to evaluate the effect of Sal B on matrix metalloproteinase-9 (MMP-9) and on the underlying mechanisms in tumor necrosis factor-alpha (TNF-alpha)-activated human coronary artery endothelial cells (HCAECs), a cell model of Kawasaki disease. Methods: HCAECs were pretreated with 1-10 mu mol/L of Sal B, and then stimulated by TNF-alpha at different time points. The protein expression and activity of MMP-9 were determined by Western blot assay and gelatin zymogram assay, respectively. Nuclear factor-kappa B (NF-kappa B) activation was detected with immunofluorescence, electrophoretic mobility shift assay, and Western blot assay. Protein expression levels of mitogen-activated protein kinase (c-Jun N-terminal kinase [JNK], extra-cellular signal-regulated kinase [ERK], and p38) were determined by Western blot assay. Results: After HCAECs were exposed to TNF-alpha, 1-10 mu mol/L Sal B significantly inhibited TNF-alpha-induced MMP-9 expression and activity. Furthermore, Sal B significantly decreased I kappa B alpha phosphorylation and p65 nuclear translocation in HCAECs stimulated with TNF-alpha for 30 min. In addition, Sal B decreased the phosphorylation of JNK and ERK1/2 proteins in cells treated with TNF-alpha for 10 min. Conclusions: The data suggested that Sal B suppressed TNF-alpha-induced MMP-9 expression and activity by blocking the activation of NF-kappa B, JNK, and ERK1/2 signaling pathways.