Abstract: The epoxy molding compounds (EMCs) were prepared by filling high thermal conductive Si₃N₄ and flame retardant Al(OH)₃ into the epoxy. The effects of two fillers on the thermal conductivity and flame retardant of the EMCs were investigated under sole and hybrid fillers filled. The experimental results show that two kinds filler of Si₃N₄ and Al(OH)₃ have similar activity on the flame retardant and thermal conductivity of the EMCs, i.e. with the increasing of filler in the epoxy, the flame retardant and thermal conductivity of the EMCs were improved to a certain extent depend on the type of fillers. Hybrid fillers have a positive effect on the thermal conductivity and flame retardant of EMCs. However, with the volume ratio of Si₃N₄ to Al(OH)₃ changing, the contribution of fillers to the thermal conductivity and flame retardant of EMC appeare cross-coupling each other. When the volume fraction of the hybrid fillers is 60% and the volume ratio of Si₃N₄ to Al(OH)₃ is 3∶2, EMCs with thermal conductivity of 2.15 W/(m·K), LOI of 53.5% and UL-94 vertical burning test ranking of V-0 was obtained.