A circuit board structure and fabrication method thereof are disclosed, including: a circuit board with a circuit layer thereon; a reactant formed on the surface of the circuit layer, wherein the reactant is an organic metallic polymer having a polymer end and a metal ion end; and a dielectric layer formed above the reactant and the circuit board, thus forming a metallic bond between the metal ion end of the reactant and the circuit layer and forming a chemical bond between the polymer end of the reactant and the dielectric layer. Owing to enhanced bonding between the dielectric layer and the circuit board, electrical performance of the circuit board structure is improved, and the demand for fine circuits is met.