Abstract: ZnS nanoparticles were synthesized and characterized.The synthetic and modified conditions of ZnS nanoparticles,such as pH value,reaction temperature,the molar ratio of Zn(Ac)₂,Na₂S and the stabilizing reagent(EDTA) and the concentration of L-cysteine,were optimized.Under the best conditions of synthesis and modification,functionalized ZnS nanoparticles with sphere shape and a diameter of 150 nm were obtained.UV-Vis,fluorescence and attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopies were used to study the interaction of ZnS nanoparticles modified by L-cysteine and Bovine hemoglobin.The results indicate that the fluorescence of functionalized ZnS nanoparticles was significantly quenched by Bovine hemoglobin.The quenching constant calculated according to Stern-Volmer equation was 1.12×10⁶ L/mol.It is inferred from this result that the effect of Bovine hemoglobin on the fluorescence of functionalized ZnS nanoparticles was a static quenching and strong interaction taking place between Bovine hemoglobin molecules and functionalized ZnS nanoparticles.The strong interaction significantly affected the second structure of BHb molecules,which was confirmed by ATR-FTIR observations.