In this study the effect of polymer/crosslinkable cogent mIxing ratio on the inflammability and dielectric properties of strontium titanate/cyclo-olefin polymer(COP) composites were investigated. To analysis the effect of COP/crosslinkable coagent mixing ratios and addition of flame retardant on the inflammability and dielectric properties, the ratio of COP/c rosslinkable coagent were varied from 90:10, to 70:30 by weight. The inflammability of composites was examined according to UL94 specification. The gel content and density of fabricated composites were investigated, and then, the dielectric property were measured at 1GHz frequency.