Abstract: Objective：To explore the influence of tumor-associated macrophages (TAMs) on the expression of matrix metalloproteinases (MMPs) and the ability of invasion and metastasis of oral squamous cancer cells. Methods：We used phorbol 12-myristate 13-acetate （PMA）and macrophage colony-stimulating factor （M-CSF）to make THP-1 monocytes differentiate into TAMs, and then we collected the culture media of TAMs as condition medium (CM) to stimulate oral squamous cancer cells. Real-time RT-PCR and Western blot were applied to detect the expression of MMPs before and after stimulation of TAMs. The ability of invasion and metastasis of oral squamous cells was measured by Transwell assays. Results：When treated with PMA and M-CSF, THP-1 cells became attached，and differentiated into TAMs. Compared to control group, the expression of MMP-2, MMP-9, MMP-13 mRNA in experimental group were up-regulated when treated with TAMs CM for 48h. Protein level of MMP-2, MMP-9, MMP-13 was up-regulated accordingly. And stimulation of TAMs CM for 24h increased invasion of oral cancer cells. Conclusions：TAMs may promote the invasion and metastasis of oral squamous cancer cells through enhancing production of MMPs.