The composite materials containing metal Ni powder of 5-15 mu m in size were prepared by use of the matrix epoxy resin of glycidyl amine crosslinked with bis-4-amino-3-methylcyclohexyl methane and 2,4-diamine 3,5-dimethyltoluene. Dynamic viscoelastic properties of the composites at various volume fraction (Phi(p)) of Ni powder have been measured over the temperature range from 30 to 300 degrees C, The peak temperatures in dynamic loss modulus-temperature diagrams of the composite increased with increasing Phi(p), although the peak position was abruptly shifted to lower temperatures in the range of Phi(p) more than 0.245. At this high concentration of Phi(p), agglomeration of the particles occurring in the composite lead to reduction of the interaction between Ni particle and epoxy resin. Parallel studies on the thermal conductivity (lambda) of the composites materials showed that the value of lambda at Phi(p) = 0.245 increased by approximately 7 times that of the original epoxy resin. The shape of Ni particles also affected the thermal durabilities of the composites; the rough surface of Ni powder yields a higher storage modulus of the composite than that of the materials containing the powder with a smooth surface, which had been brought through a ball-milling process. The finding suggested that the increasing in specific surface area of the powder improved the thermal durability of the composites as well as their mechanical properties.