Objective: Immune cells in the tumor microenvironment not only fail to mount an effective anti-tumor immune response, but also interact intimately with the transformed cells to promote oncogenes actively. Signal transducer and activation of transcription Stat 3 gene expression in M2 macrophages increases tumor cell proliferation, survival and invasion while suppressing anti-tumor immunity as well as cancer stem cell activation. The persistent activation of STAT3 also mediates tumor-promoting inflammation. Genetic studies demonstrate that ablation of the Stat3 gene in either tumor cells or tumor-associated macrophages and other immune cells, even under chronic inflammatory conditions, inhibits carcinogenesis as well as the growth of established tumors. Materials and Methods: In this study, murine macrophage J774 A.1 cell line was used as a typical mouse macrophage for evaluation of Stat3 gene expression in mRNA level. Culture condition followed by DMEM supplemented with 10% fetal bovine serum. Total RNA was extracted and converted to cDNA. PCR was performed by Stat3 primers and then gene expression was evaluated by gel electrophoresis. Beta-actin was used as an internal control. Results: Gel electrophoresis data was shown Stat3 expression in murine J774 A.1 macrophage cell line. Conclusion: Previous studies have been shown the ablation of the Stat3 gene in m2 macrophage caused to cancer stem cell inactivation. As regards Stat3 was expressed in J774 A.1 cell line thus it seems that this cell line can be used for knockdown studies in order to cancer stem cell inactivation.