Abstract: By using axially di-substituted silicon(IV) phthalocyanine (SiPc) as fluorescent monomer, which was synthesized through the reaction of silicon (IV) phthalocyanine dihydroxide with 3-(trimethoxysilyl) propyl methacrylate, potassium persulfate as initiator, and sodium dodecyl sulfate as emulsifier, a novel monodispersed polystyrene fluorescent microsphere (hereafter called as P(St-co-SiPc)) was prepared via in-situ copolymerization. The surface morphology and composition of the as-prepared microspheres were characterized by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). The optimized synthetic conditions had also been explored. It was found that both the size and monodispersity of P(St-co-SiPc) increased with the temperature increasing (from 60℃ to 70℃). When the experimental temperature reached up to 75℃, the diameter of P(St-co-SiPc) started to decrease, followed by broadening of the particle size distribution. The same trend was also observed with the fluorescence emission of P(St-co-SiPc). In the case of a given amount of one monomer, whatever monomer (styrene or SiPc) was used, the amount of another monomer had the similar influence on the surface morphology of the microsphere. The size of the microspheres increased with increasing amount of the monomer used. The monodispersity and fluorescence intensity of P(St-co-SiPc) were closed to a best value when the amount of the monomer was in the range of 6~8 mL for styrene and 5~15 mg for SiPc. By using diphenylanthracene (DPA) as a singlet oxygen indicator, the photosensitivity of P(St-co-SiPc) was evaluated by UV-Vis absorption spectroscopy. As a result, these microspheres exhibited very good photosensitivity. Upon excitation with 640 nm laser, the UV-Vis absorption intensity of P(St-co-SiPc) increased quickly in the presence of DPA. On the other hand, if no irradiation was applied to the above system, its absorption intensity was found to keep unchanged. These findings would have important reference value for controllable etching.