Allylester resin tethered to layered silicate was synthesized by in-situ polymerization method and was cured by tert-butylperbenzoate (TBPB) directly. We ascertained the existing of carbonyl and benzyl groups which come from diallyl terephtalate in the gallery of layered silicates using the thermogravimetric analysis (TGA) and FT-IR. The residual weight and new IR peaks of the clay, which is treated by in-situ polymerization, imply that the hydroxy group of intercalant takes part in the polymerization of allylester resin. Also, its nanocomposite was characterized by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns and TEM photographs indicate that the basal spacing (d(001)) of the nanocomposite made by in-situ polymerization is larger than those of the nanocomposite made by a simple mixing.