Abstract: Objective To study the inhibitory effect of small interfering RNA(siRNA) targeting CXCR4 gene in EC9706 cells. Methods We designed two siRNAs against CXCR4 gene.Two siRNAs were transfected into EC9706 cells with lipofectamine,respectively.The expression level of CXCR4 mRNA in each group was detected by real-time PCR ; the effect of CXCR4 on the cell cycle was observed by flow cytometry; the effect of CXCR4 on the growth of the cells was observed by MTT method. Results Compared with empty vector control group and untransfected group, the mRNA level of CXCR4 in siRNA transfected group was obviously reduced,and the growth speed of cells was lower, S phase proportion cut down in EC9706 cells transfected with pRNAT-U6.2/Lenti- siCX1,the exercise performance of the cells cut down in siRNA transfected group cells. Conclusion RNA interference can effectively inhibit CXCR4 expression, which plays an important role in inhibiting the growth and metastasis of the tumor.