Abstract: Mesoporous silica nanoparticles(MSN)were synthesized under alkaline conditions using tetraethoxysilane(TEOS)as silica source, hexadecyl trimethyl ammonium bromide(CTAB)as template agent, ethanol as co-solvent and triethanolamine as chelating agent. Ammonia propyl and folic acid(FA)were then modified on the surface of MSN in two consecutive steps. The morphology and structure were characterized, and the loading amount of realgar was determined by atomic fluorescence spectrometry. Results showed that the MSN had large specific surface area(973 m²/g)and pore volume(1. 01 cm³/g), narrow pore size distribution, uniform particle size(about 90 nm)and well-dispersed spherical morphology. The assayed loading ratio of realgar in FA- modified MSN reached the maximum(2. 52%)in 0. 5 h. Hence, it was shown that the MSN-NH-FA has good morphology and favorable structure which is suitable as a drug carrier and hold potential in the application.