The invention relates to a composite material, a high frequency circuit substrate made of the composite material and a preparation method of the composite material. The composite material comprises the following solid components: 10-70 parts by weight of DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) derivative compounds, 10-50 parts by weight of a curing agent, 10-90 parts of one or more epoxy resin and 10-40 parts by weight of an inorganic filling material; the halogen-free low-dielectric resin composition provided by the invention adopts the high-purity DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) derivatives which are dispersed in the composition in the form of fine particles, so that not only is the cross-linking degree of the composition not reduced, but also the heat resistance and the flame resistance are improved; besides, a PCB made of the resin composition adopts prepregs and copper clad laminates, thereby having excellent dielectric property and high glass transition temperature, being able to meet the high speed requirement of the printed circuit CCL (copper-clad plate) industry for high frequency electronic signal transmission and information processing.