To determine the effects of exogenous LKB1 gene on biological behavior of lung carcinoma cells.Nest PCR was used to clone LKB1 gene pcDNA-LKB1 and pcDNA3.1 were introduced into A549 cell line by lipofectin transfection, and the A549 cells stably expressing LKB1 gene were established by G418 selection. The expression of LKB1 and STAT3 protein was detected by Western blot. Cell proliferation was observed by growth curve and clone formation. Cell cycle and apoptosis were assayed by flow cytometry(FCM).A549 cells stably expressing LKB1 protein were established. Compared with the vector transfected cells, the positive clone cells grew more slowly. FCM showed that more positive clone cells went into phase G0/G1 and fewer cells went into phase S. Moreover, there was significant difference on apoptosis between the two group cells.LKB1 protein might inhibit malignant biological behavior of A549 cells partly by down-regulating the tyrosine-phosphorylated level of STAT3 protein.