N, N'-4, 4'-bimaleimide diphenyl methane (BDM), diallylbisphenol A (DBA) and hyperbranched polysiloxane (HBPsi) are performed to fabricate the BDM/DBA/HBPSi composites by one-step method. The contents of HBPSi affecting on the mechanical, thermal and dielectric properties of the BDM/DBA/HBPSi composites are investigated. Results show that the appropriate incorporation of HBPSi into BDM/DBA not only significantly improves the toughness, but also improves the heat resistance and dielectric properties of the BDM/DBA/HBPSi composites. The outstanding comprehensive properties of BDM/DBA/HBPSi composites indicate great potentiality in fabricating advanced polymeric composites.