Objective To investigate the effect of PDS5B on the biological function of A549 human lung cancer cells and possible molecular mechanism. Methods The proliferation of lung cancer cells was detected by MTT assay and colony formation assay after silencing or overexpressing PDS5B of A549 cells. The cell migration was detected by scratch assay and TranswellTM assay. The protein expression of PDS5B and Wnt5a in A549 cells was detected by Western blot analysis. Cell migration was detected by TranswellTM after PDS5B small interference RNA(siRNA) and Wnt5a siRNA were co-transfected. Results Compared with the negative control group, the protein expression of PDS5B decreased significantly after transfected with PDS5B siRNA. The proliferation ability , colony formation rate and migration ability of A549 cells significantly improved, and the expression of Wnt5a was increased. The opposite results were observed after PDS5B over-expression. The co-transfer experiment showed that Wnt5a could resist the inhibition of A549 cells by PDS5B. Conclusion PDS5B inhibits lung cancer cell proliferation by down-regulating Wnt5a expression.