The invention relates to a composite material and a high-frequency circuit substrate made from the composite material. The composite material includes: a thermosetting composition in an amount of 20 to 70 by weight with respect to the composite material, a fiberglass cloth processed by a coupling agent; a powder filler; a fire retardant and a cure initiator. The thermosetting composition includes a resin with molecular weight thereof being less than 11,000, and a low-molecular-weight solid allyl resin. The resin is composed of carbon and hydrogen elements. More than 60 percent of the resin is vinyl. The high-frequency circuit substrate made from the composite material comprises: a plurality of prepregs mutually overlapped and copper foils covered on both sides of overlapped prepregs, wherein each prepeg is made from the composite material.