Aim To investigate the effect of Tanshinone ⅡA on endothelial cells’ cyclooxygenase-2 （COX-2） expression and the relative mechanisms. Methods Human aortic endothelial cells were incubated in vitro and then co-cultured with angiotension Ⅱ （100 nmol/L）,Tanshinone ⅡA （1 μmmol/L） and no drugs respectively for 10 minutes,1 hour and 2 hours.The expressions of COX-2 mRNA were measured by real time-PCR and COX-2,p38MAPK,p-p38MAPK,NF-κB and p-NF-κB protein levels were measured by Western blot assay. Results AngiotensionⅡ could induce the expression of COX-2 mRNA and protein （P<0.01） as the same as the phosphorylation of p38MAPK and NF-κB （P<0.01）.Incubating human aortic endothelial cells with angiotensionⅡ and Tanshinone ⅡA suppressed the expression of COX-2 （P<0.01） and the phosphorylation of p38MAPK and NF-κB was also decreased （P<0.01）. Conclusion Tanshinone ⅡA could suppress the expression of COX-2 and it may be achieved through inhibiting the phosphorylation of p38MAPK and NF-κB.