A thermosetting resin composition is provided. Styrene type polyphenylene ether of which a terminal group is subjected to styrene modification and acrylic-type polyphenylene ether of which a terminalgroup is subjected to acrylic modification are employed as main resins, and the weight ratio of the two kinds of polyphenylene ether ranges from 0.5 to 1.5, and therefore the thermosetting resin composition has excellent heat resistance, flowability and glue filling performance. Furthermore, many kinds of hyperoxide having different half-life temperatures is employed to form a compound cross-linking initiator, and the cross-linking density during the thermal hardening process can be effectively improved. The hardened thermosetting resin composition has low dielectric constant, low dielectric loss, high Tg and high rigidity, and is applied to reinforcing material dipping to form prepreg, and the prepreg has excellent cutting performance.