Objective: To explore the mechanism of miR-155 promoting the expression of PDCD4 in macrophages through the signaling pathway of SOCS1/STAT3. Method: The target of miR-155 was predicted on the Targerscan website and tested by the SCOS1-containing fluorescent reporter gene. MiR-155 and Anti-miR-155 were transfected into macrophage RAW264.7, and the expression levels of SCOS1 and pSTAT3 protein were detected by Western blotting. Mouse macrophage RAW264.7 was infected with SOCS1 overexpressing virus and empty virus, respectively, and the SOCS1 expression level was detected by real-time PCR. Mouse macrophage RAW264.7 was transferred with STAT3 siRNA, and the protein expression of pSTAT3 was determined by Western blotting. In four differently treated mouse macrophages, Western blotting was utilized to detect SCOS1, pSTAT3 and PDCD4. Result: The SCOS1 gene is a target gene of miR-155. The expression levels of SOCS1 significantly decreased and p-STAT3 increased after miR-155 transfection compared with untransfected macrophages (P<0.05). In contrast, the expression levels of SOCS1 significantly increased and p-STAT3 decreased after anti-miR-155 transfection. The gene expression of SOCS1 significantly increased after SOCS1, over-expressing virus infection (Adv.SOCS1) (P<0.05) compared with the mouse macrophage RAW264.7, which was not infected with any virus. The expression of pSTAT3 protein was significantly decreased compared with untransfected cells in STAT3 siRNA transfected mouse macrophage RAW264.7 (P<0.05). The expression of SCOS1 protein in cells treated with ox-LDL alone was significantly lower (P<0.05), and the expression of pSTAT3 and PDCD4 protein significantly greater, than in untreated cells (P<0.05). Conclusion: MiR-155 promotes the expression of PDCD4 in macrophages through the SOCS1/STAT3 signaling pathway.