Disclosed are an alkoxysilylated isocyanurate epoxy compound, a composite of which exhibiting low CTE and high glass transition temperature or Tg-less and/or a cured product of which exhibiting good flame retardant property, a method of preparing the same, a composition including the same, a cured product formed of the composition, and a use of the composition. An isocyanurate epoxy compound having an alkoxysilyl group and an epoxy group in a core; a method of manufacturing the epoxy compound by the epoxidation and alkoxysilylation of a starting material; an epoxy composition including the epoxy compound; and a cured product and a use thereof, are provided. A composite of the epoxy composition has improved bonding efficiency between alkoxysilyl group and filler and between alkoxysilyl groups, and has good heat resistance, low CTE, and high glass transition temperature or Tg-less. A cured product formed of the epoxy composition has good flame retardant property.