Abstract: Multi-walled carbon nanotubes (MWCNTs) treated with mixed acids were used to reinforce the bisphenol A cyanate ester-novolac cyanate ester(BCE-NCE) resin. The microstructure of the MWCNTs/BCE-NCE composites was characterized by SEM and TEM. The thermal performances of the MWCNTs/BCE-NCE composites were investigated by DSC, DMA and TG/DTA. The mechanical properties of the MWCNTs/BCE-NCE composites were investigated by electronic tension machine. The dielectric properties of the MWCNTs/BCE-NCE resin were investigated by cavity resonator method. The results show that the dispersion properties of the treated MWCNTs in the BCE-NCE resin matrix are improved compared with the untreated analogue. MWCNTs have little effect on the BCE-NCE resin thermodynamic properties. Upon addition of 0.8wt% MWCNTs to the BCE-NCE resin, the glass transition temperature(T_g) of the cured MWCNTs/BCE-NCE composites changes from 298℃ to 285℃, maintaining a relatively high value. The BCE-NCE resin impact strength of 0.6wt% MWCNTs is 11.40 kJ/m², and the toughness increases by 40.7%. The dielectric constant and dielectric loss of MWCNTs/BCE-NCE composites increase obviously. Upon addition of 0.8wt% of MWCNTs to the resin, the dielectric constant is 5.1 and dielectric loss is 0.032 under 1 GHz frequency. Therefore, the MWCNTs/BCE-NCE composites may be suitable for future applications involving high performance composites and electronic industry.