Abstract: Objective To investigate the influence of nm23-H1 gene transfection on the expressions of matrix metalloproterinase 9（MMP-9）and tissue inhibitor of metalloproteinase 1（TIMP-1） in lung cancer cells. Methods nm23-H1 gene was transfected into lung cancer cell line L9981 by gene transfection technology. SemiRT-PCR was used to detect the different mRNA expressions of TIMP-1 and MMP-9 between transfected and nontransfected lung cancer cell lines. Flow cytometry was used to detect the different protein expressions of TIMP-1 and MMP-9 between transfected and non-transfected lung cancer cell lines. Results The mRNA and protein levels of TIMP-1 in transfected lung cancer cell lines were stronger than those in non-transfected lung cancer cell lines. The mRNA and protein levels of MMP9 in transfected lung cancer cell lines were weaker than those in non-transfected lung cancer cell lines. Conclusion The nm23-H1 gene can up-regulate expressions of TIMP-1 and down-regulate expressions of MMP-9 in lung cancer cell line L9981.