Disclosed are an epoxy compound having an alkoxysilyl group, a composite of which exhibits good heat resistant properties and/or a cured product of which exhibits good flame retardant properties, a method of preparing the same, a composition comprising the same, and a cured product and a use of the composition. An alkoxysilylated epoxy compound comprising at least one of Chemical Formula S1 substituent and at least two epoxy groups in a core, a method of preparing the epoxy compound by an allylation, a claisen rearrangement, an epoxidation and an alkoxysilylation, an epoxy composition comprising the epoxy compound, and a cured product and a use of the composition are provided. The composite of the disclosed exhibits improved chemical bonding, good heat resistant properties, a low CTE, a high glass transition temperature or Tg-less. The cured product of the composition exhibits good flame retardant properties.