Spray pyrolysis was applied to prepare spherical silica particles with mesopores of a regular structure. The physical properties such as surface area, pore size, pore structure, particle size, and morphology were studied by BET, SEM, SAXS, and DLS analysis. At a fixed gas flow rate, the BET surface area changed from 200 to 1,290 m2/g as changing the CTAB/TEOS molar ratio from 0.05 to 0.3. At a fixed CTAB/TEOS ratio, the surface area of silica particles was varied from 1,062 to 1,305 m2/g with changing the gas flow rate from 10 to 40 l/min. The average pore size measured by BJH desorption was about 21~23 A and not significantly influenced by the CTAB/TEOS ratio and the gas flow rate. Finally, the highest surface area which was 1,305 m2/g were obtained when the CTAB/TEOS ratio and the gas flow rate were 0.2 and 20 l/min, respectively. According to SAXS analysis, the prepared silica particles showed a strong peak at 2θ=2.6o and two minor peaks around 2θ=4.4o and 5.1o, which are due to regular mesopores of hexagonal structure. The morphology of silica particles prepared were spherical shape and the average particle size was 1.0 μm.