Preparation of micrometer-sized spherical particles containing Rhodamine 6G (R6G) has been investigated for spherical cavity structure. Hydrolysis and polymerization processes of phenyltriethoxysilane (PTES) as a starting material was pursued by observing the change of PTES/R6G in HCl solution with its optical absorption and viscosity. As the polymerization of PTES proceeded, increase of molecular size resulted in change its properties from hydrophilic to hydrophobic, and subsequently the solution separated into two layers of aqueous and organic. Polymerized PTES in the organic layer showed good affinity with incorporated R6G, and high monomer/dimer ratio in particles was achieved. Moreover, using them intermixing of unsuitable particles of submicron size was avoided, because hydrolyzed PTES of small molecular size that is the origin of submicron-sized particles was removed to the aqueous layer. With stirring, titration of diluted droplets containing polymerized PTES was suitable for preparing several micrometer sized particles, and followed by solidification in ammonia water. Degree of the polymerization of PTES and viscosity of liquid droplets were the key factors for determining the properties of R6G-doped spherical particles of optical cavity structure.