To investigate the effects of CD137 signaling on the regulation of CD3-CD56+NK cells function. Methods: CD3-CD56+NK cells were treated with CD137 mAb or mouse IgG1 isotype control to study the effects of CD137 signaling on the function of CD3-CD56+NK cells. Cytotoxicity was measured by LDH activity in the supernatants of cell cultures; NKG2D and LFA-1 expression on CD3-CD56+NK cells were analyzed by flow cytometry. Results: CD137 was expressed on activated CD3-CD56+NK cells. The CD137 mAb enhanced the ability of CD3-CD56+NK cells to kill lung cancer cells(A549)；Further studies revealed that the expression of NKG2D and LFA-1 was significantly increased in activated cells, and blockade of NKG2D and LFA-1 dramatically attenuated CD3-CD56+NK cytolysis of A549 cancer cells. Conclusion: CD137 signaling increases the ability of CD3-CD56+NK cells to kill cancer cells via up-regulating the expression of NKG2D and LFA-1.