The present invention relates to a thermosetting resin composition for a high speed transmission circuit board, more particularly to a thermosetting resin composition having superior dielectric characteristics with low dielectric constant and dissipation factor and having superior glass transition temperature, heat resistance after moisture absorption, dielectric reliability, adhesion to copper film, workability, dispersibility of inorganic filler, electric characteristics, etc., and thus being useful for a copper clad laminate for high speed signal transfer.