Polysiloxane microspheres (PSM) were prepared from a linear siloxane polymer by a simple emulsion procedure. Then, novel modified polysiloxane microspheres (MPSM) containing Si-OH groups were generated by introducing of organic hindered phenol groups, which were exploited for the functionalization of the microspheres with hydroxyl groups. The structure and properties of PSM and MPSM were revealed by various analysis, such as FTIR, XRD, SEM, TG, BET, etc. These polysiloxane microspheres, PSM and MPSM, were then used as rubber reinforcing fillers. The PSM and MPSM offered obvious effects on the properties of chlorinated butyl rubber (CIIR) and can improve its damping performance in a different agree. In addition, thermal stability, thermal conductivity, tensile properties, and toughing and damping mechanisms of the rubber composites were also investigated. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.