In this work, an experimental study was conducted to improve mechanical and electrical insulating properties of room temperature vulcanized silicone rubber (RTVSR) matrix by incorporating hollow silica spheres (HSS). The results showed that the addition of 5.0 wt% HSS in the RTVSR matrix noticeably improved the tensile strength. The volume resistivity of RTVSR nearly increased by one order of magnitude and the DC breakdown strength of RTVSR almost doubled when 5.0 wt% HSS were added. In contrast, commercial fumed silica (FS) with nanometre size showed relatively weak enhancing effects on RTVSR both in mechanical and electrical insulating performances at the same loading. (C) 2017 Elsevier B.V. All rights reserved.