Abstract: Three different POSS (4-(2-Ferrocenylethenyl)-phenyl-heptacyclopentyl-POSS(POSS1), acryloisobutyl-POSS(POSS2), aminopropylcyclopentyl-POSS(POSS3)) were respectively added into styrene and POSS/polystyrene composites were prepared by bulk free radical polymerization. The dispersion quality of POSS in the matrix of polystyrene was characterized by XRD and TEM. The results indicate that some POSS1 particles in the POSS1/PS are presented in stripe figure. POSS2 is completely dispersed at molecular level in PS matrix, while aggregated POSS3 particles can be seen in POSS3/PS. TGA data indicate that the thermal stabilities of three POSS/PS composites are obviously improved compared to neat PS, and that of POSS1/PS composites are prior to the others. Glass transition temperatures (T_g) of POSS1/PS and POSS2/PS composites are respectively increased by 10℃ and 8℃ in comparison with the neat PS. 