A thermosetting resin composition and a prepreg and a laminated board prepared therefrom. The thermosetting resin composition contains the following components in parts by weight: 50-150 parts of a cyanate; 30-100 parts of an epoxy resin; 5-70 parts of styrene-maleic anhydride; 20-100 parts of a polyphenyl ether; 30-100 parts of a halogen-free flame retardant; 0.05-5 parts of a curing accelerator; and 50-200 parts of a filler. The prepreg and laminated board prepared from the thermosetting resin composition have comprehensive performances such as a low dielectric constant, a low dielectric loss, an excellent flame retardance, heat resistance and moisture resistance, etc., and are suitable for use in a halogen-free high-frequency multilayer circuit board.