Abstract: The mesocarbon microbeads (MCMBs) with different size and fabrication process (M22, M15 and M23) were fabricated cyanate ester resin (CE) (MCMBs/CE) composites with volume fraction of 10vol%, 25vol%, 40vol% and 50vol% of MCMBs. The MCMBs/CE composites were characterized by SEM, XRD, Raman spectrum, thermal analyzer and resistance instrument. The results indicate that all the three spherical powders have the graphitization structure. Compared to M15 and M23, the M22 filler shows a regular spherical particle, the highest carbonization (I_D/I_G=0.23) and the lowest volume resistivity. The moisture resistance, thermal conductivity and electrical conductivity of the MCMBs/CE composites are enhanced with the increasing of fillers volume fraction. While, the impact strength of composites presents a marginal reduction with further increase in filler content. The MCMBs/CE composite achieves a low water absorption of 0.45%, a high impact strength of 23.6 kJ/m², a high thermal conductivity of 1.28 W/(m·K) and a low volume resistivity of 1.5 Ω·cm containing 40vol% M22 filler.