We have prepared nano size mesoporous silica using sol-gel reaction and incorporated fluorescent dye inside the silica network, and investigated fluorescent properties of the particles. Monodisperse core silica has been prepared via sol-gel reaction of TEOS (tetraethoxysilane) and water using base catalyst. The SEM images of silica cores showed that most particles were uniform and spherical with particle diameters of 187 nm. Mesoporous core-shell structure of silica with shell was prepared via further reaction with C(18)-TMS (octadecyltrimethoxysilane) and heat treatment. The SEM image of core-shell silica shows that the average diameter is 305 nm and the thickness of shell is 118 nm. The size of silica particles was measured by electrophoretic light scattering system (ELS-8000, Otsuka). The pore volume and surface area were increased after calcination. A typical value for the specific surface area, calculated according to the BET (Brunauer-Emmett-Teller) method from nitrogen isotherms is as 400 m(2)/g. Fluorescein isothiocyanate (FITC) could be incorporated into the silica network by coupling reaction with organic functionalized silane. The optical properties of the particles were characterized with UV/Vis spectrometer and PL spectrometer.