Disclosed are mesoporous silica particles and a preparation method thereof, particularly, a method of preparing mesoporous silica particles, including mixing a silica precursor, an alkylamine-based surfactant, and a phosphoric acid-based cosurfactant, thus preparing a mixture solution (a mother liquor); adding or not adding the mixture solution with an acid solution, and conducting stirring, thus providing mesoporous silica particles; and thermally treating the mesoporous silica particles. These mesoporous silica particles are prepared using a phosphoric acid-based cosurfactant for stabilizing the surface of the particles to prevent the aggregation thereof, thereby uniformly distributing the particles. Through a hydrothermal reaction, the mesoporous silica particles have various pore sizes, a large surface area, and a high pore volume, and thus are widely used in catalysts, adsorbents, low dielectrics, and separation and purification processes, and are useful as templates for the preparation of novel porous materials, including porous carbon.