CdSe/TiO₂composite nanoparticles were synthesized by ultrasounddriven approach and characterized by SEM，TEM，XRD，UVVis and FS．The visible light photocatalytic activities of CdSe/TiO₂ on leukemia HL60 cells were investigated by CCK-8 approach and the ultrastructural morphology of HL60 cells was also studied by SEM．The  experimental results indicated that an obvious inhibition of leukemia HL60 cells growth would be observed in groups treated with CdSe/TiO2 composite nanoparticles，and the PDT effiency in  the presence of CdSe doped TiO₂ was significantly higher than that of TiO₂，revealing that the visible light photocatalytic activities of TiO₂ could be efficiency enhanced by the modification of CdSe．Additionally，CdSe/TiO₂ can exhibit a very high photodynamic efficiency of 76% at a final indicated concentration of 4 μg/mL under visible light irradiation．The fluorescence spectrum analysis shows that the CdSe/TiO₂ composite nanoparticles could improve the photocatalytic activity of the composite nanoparticles by separating the photogenerated hole pairs，thus enhancing the PDT inactivation efficiency of HL60 cells．