Objective To investigate tumor cell killing effect of superparamagnetic Fe3O4 nanoparticles with cubic phase through magneto-mechanical force under a low-frequency vibrating magnetic field ( VMF). Methods A kind of strong magnetic and irregular-shaped Fe3O4 nanoparticles with cubic phase was synthesized by coprecipitation method. The Fe3O4 nanoparticles were exposed to a self-developed VMF and cell killing efficiency of the Fe3O4-mediated magneto-mechanical force was investigated. Results VMF alone had no effects on cell viability. After Fe3O4 nanoparticles were added, the cell viability significantly decreased with prolonging the VMF treatment time and increasing the Fe3O4 nanoparticle concentration. Lactate dehydrogenase released by damaged cells also increased with prolonging the VMF exposure time. Conclusions The irregular-shaped Fe3O4 nanoparticles can transfer magneto-mechanical force to tumor cells under VMF, cause structural damage of cells and result in cell death. The VMF generator developed in this study has simple structure and it is safe for use and convenient for operation. The developed magnetic nanoparticles and the corresponding cancer cell killing technique have the potential for clinical transformation.