A new photosensitizer 5ALATSFA was synthesized through the combination of cancer targeting molecule folate (FA), silica coated TiO2 (TS) nanoparticles and 5aminolevulinic acid (5ALA). Photodynamic therapy efficiency of 5ALATSFA on leukemia HL60 cell was studied in this paper. The composite nanoparticles (5ALATSFA) was synthesized by surface modification method and was characterized by transmission electron microscope (TEM), fourier transformation infrared spectrum (FTIR), ultravioletvisible absorption (UVVis) and so on. HL60 cells were cultured with different concentrations of composite nanoparticles 5ALATSFA for 12 h. The dark toxicity and PDT inactivation effect of nanoparticles were detected by Cell Counting Kit8 (CCK8) method. The experimental results show that the dispersibility of 5ALATSFA composite nanoparticles is good. When 5ALATSFA is incubated with HL60 cells for 12 hours at a concentration of 100 μg/mL, the dark toxicity of 5ALATSFA to HL60 cells is low and the 5ALATSFA inactivation efficiency of photodynamic therapy can reach 74.65%, which is significantly higher than that of TiO2 and TSFA. Therefore, 5ALATSFA has a good prospect of application as a potential photosensitizer.