Aim To investigate the effects of the scavenger receptor A_Ⅰ( SR A_Ⅰ) on expression of matrix metalloproteinase 2 (MMP 2) and matrix metalloproteinase 9 (MMP 9) and its tissue inhibitor of metalloproteinase (TIMP) in macrophage drived foam cells. Methods THP 1 cells were incubated with PMA, then added oxidized low density lipoprotein (ox LDL) to induce macrophage cell foaming. Foamed macrophage cells were verified by oil red staining and high performance liquid chromatography (HPLC). Scavenger receptor A_Ⅰ mRNA was detected by reverse transcriptase polymerase chain reaction (RT PCR). Antisense and antibody were used to block SR A_Ⅰin foamed cell. MMP 2, MMP 9, TIMP 1 and TIMP 2 were detected by Western blot. MMP 2 and MMP 9 activities in media were estimated using zymography. Results Blocking SR A_Ⅰinhibits activities and expression of MMP 2 and MMP 9, increases the expression of TIMP 1 and TIMP 2. Conclusions Blocking the activities of SR A_Ⅰmay contribute to maintain the balance between MMP and TIMP and inhibit macrophage mediated matrix breakdown in the atherosclerotic plaques.