C-doped TiO2 nanoparticles combined with g-C3N4 were prepared by chemical vapor deposition, using X-ray diffraction, fluorescence spectroscopy, transmission electron microscopy, UV-Vis absorption spectroscopy and energy dispersive spectrometer to characterize nanoparticles. The effects of g-C3N4@C-TiO2 nanoparticles on HL60 cells in vitro were explored in dark and under light irradiation. Cell Counting Kit-8 (CCK-8) method was used to investigate the viability of HL60 cells treated with nanoparticles with a series of concentration gradients, and the level of intracellular reactive oxygen species was detected via fluorescent probe labeling technology. The experimental results showed that by modifying g-C3N4 on the surface of C-TiO2, the absorption wavelength range of TiO2 could be extended to the visible band. The particle size of g-C3N4@C-TiO2 prepared was about 10～20 nm, which met the size requirement of entering cells. Dark toxicity experiment proved that g-C3N4@C-TiO2 nanoparticles were less toxic to cells under darkroom conditions, which suggested they had good biocompatibility. Meanwhile, compared with the groups treated?with?TiO2 and C-TiO2?nanoparticles, the photocatalytic inactivation efficiency of the group treated with g-C3N4@C-TiO2 was as high as (76.5±1.9)% under light irradiation, indicating its potential as a potential photosensitizer for the treatment of leukemia.