Aim To study whether lipopolysaccharide(LPS) regulates the production of matrix metalloproteinase 1(MMP 1) and tissue inhibitor of matrix metalloproteinase 1 (TIMP 1) in fetal aortic smooth muscle cells. Methods Aortic smooth muscle cells from 4～6month healthy abortive fetuses were incubated for 72 h with various concentration of LPS in vitro (0, 5, 10, 25 mg/L). The concentration of MMP 1 and TIMP 1 in the concentrated culture media was measured by Western Blotting. Results Compared with the control group, LPS could inhibit the production of MMP 1 in the smooth muscle cells, but could not change the production of TIMP 1 in the smooth muscle cells. Conclusions LPS could not promote the rupture of the atherosclerotic plaques by destroying the balance of the MMP 1 and TIMP 1 in the smooth muscle cells.