The changes of structure and physical properties of the particulate composites which were made of PET filled with SiO2 in various contents have been studied. The matrixes and fillers were mixed in the state of solution and molded by compression press. Measurements were carried out with Instron for mechanical properties, Rheometre for dynamic visco-elastic properties, D.S.C. for thermal properties, X-ray diffractometer for crystallinity and crystallite size, respectively. The results obtained are as follows; As the filler contents increased, yield stress and tensile strain decreased, the peak region of tan$delta$ broadened and the values of G below glass transition region increased, and the crystallization temperatures lowered. Furthermore, it was supposed that the crystallinity increased due to the increase of the number of crystallites on account of the formation of nuclear of the spherullites as the fillers were mixed, and that the growth of the crystallites were hindered by the excess contents of the fillers.