The present invention relates to an alkoxysilylated epoxy compound, a composite exhibiting good heat resistance properties, low CTE and high glass transition temperature and not requiring a coupling agent, a composition including the same, a cured product formed of the composition, a use of the cured product, and a method of preparing the epoxy compound having alkoxysilyl group. An epoxy compound having an epoxy group and an alkoxysilyl group, a composition including the epoxy compound, a curing agent, a filler and/or a reaction catalyst, a cured product of the composition, and a use of the composition including an electronic part are provided. In a composite and/or cured product, the epoxy composition exhibits improved heat resistance properties, decreased CTE, and increased glass transition temperature or Tg-less. The cured product exhibits good flame retardant properties by the introduction of the alkoxysilyl group.