Aim To observe the effect of granular-macrophage colony stimulating factor (GM-CSF) on the expression and activity of matrix metalloproteinases (MMP). Methods Human endothelial cells were cultured in vitro and the protein expressions of MMP-2 were detected by Western blot. MMP-2'activity was detected by Zymography. Results The results revealed that the protein expression and activity of MMP-2 were significantly increased after endothelial cells were stimulated by GM-CSF. And the protein expression and activity of MMP-2 were in a dose-dependent and time-dependent manner. Conclusions The results indicate that GM-CSF can obviously increase the protein expression and activity of MMP-2 in human endothelial cells. So GM-CSF could enhance the breakdown of matrix in lesions of atherosclerosis which could probably induce vulnerable plaque.