Provided are an alkoxysilylated epoxy compound, a composite of which exhibits good heat resistance properties, particularly low CTE and increased glass transition temperature, and a cured product thereof exhibits good flame retardancy and composition of which does not require additional silane coupling agent, a method for preparing the same and a composition and a cured product including the same. An alkoxysilylated epoxy compound including at least one alkoxysilyl group and at least two epoxy groups, a method for preparing the same by epoxide ring-opening reaction of starting material and alkoxysilylation, an epoxy composition including the epoxy compound, and a cured product and a use of the composition are provided. Since chemical bonds may be formed between alkoxysilyl group and filler and between alkoxysilyl groups, chemical bonding efficiency of the composite may be improved. Thus, the composite exhibits good heat resistance properties and the cured product exhibits good flame retardancy.