Polymer-ceramic dielectric composites, which possess better dielectric properties, flexibility, ease in processing and shaping since they combine the advantages of polymers and dielectric ceramics, are widely used in microwave substrate applications. In order to optimize the properties of the composites, it is necessary to enhance the compatibility between the polymer matrix and ceramic filler because of their tremendous difference. In this paper, the vinyltrimethoxysilane (VTMS) is used to modify the Ba(Mg1/3Nb2/3)O-3 (BMN) ceramic particles which can improve the compatibility between BMN ceramics and PTFE and the distribution of BMN in polytetrafluoroethylene (PTFE). The modification of VTMS has no influence on the crystal structure of BMN ceramics and the compact VTMS modified BMN/PTFE composites with satisfactory uniformity and less cavities are obtained. The relative permittivity (Er) of VTMS modified BMN/PTFE composite substrate is 5.84 while the loss tangent reaches 1.5 x 10(-3) at microwave frequencies (around 10 GHz). (C) 2017 Elsevier B.V. All rights reserved.