In this paper, BiFeO₃@TiO₂ composites nanoparticles were synthesized by solgol method. The nanoparticles were characterized by transmission electron microscope (TEM), Xray diffraction (XRD), fluorescence emission spectrum etc. The Cell Counting Kit8 (CCK8) method was used to detect the activity of HL60 cells treated with a final concentration of 50 μg/mL nanoparticles under the action of weak stable magnetic field with different strengths in dark room and light conditions. The experimental results showed that the viability of HL60 cells treated with BiFeO₃@TiO₂ composites nanoparticles for 12 hours at a concentration of 50 μg/mL increased from 78% to 85%, with the increment of TiO₂ shell thickness in the darkroom condition. However, cell groups treated by BiFeO₃@TiO₂ composites nanoparticles with a mass ratio of BiFeO₃ to TiO₂of 1∶2 showed the highest cell inactivated efficiency of 78% under light exposure. The weak stable magnetic field enhanced the PDT inactivation efficiency of HL60 cells.Therefore,it provides a reference for the clinical application of photodynamic therapy in the treatment of tumor cells under weak stable magenetic field.