Disclosed are a thermosetting resin composition, a prepreg made therefrom, a laminate clad with a metal foil, and a high-frequency circuit board, wherein the thermosetting resin composition contains thermosetting ingredients. The thermosetting ingredients include a phosphorus-containing monomer or a phosphorus-containing resin and a polyphenylene ether resin containing an unsaturated group, and the phosphorus-containing monomer or the phosphorus-containing resin has a structure as shown in formula I. By using the phosphorus-containing monomer or the phosphorus-containing resin as a cross-linking agent of the polyphenylene ether resin containing an unsaturated group and by means of a cross-linking reaction of a large number of unsaturated double bonds in the resin, the high-frequency dielectric properties and high-temperature-resistance required by a circuit substrate are provided.