Abstract: Copper/graphite composites are widely used in rail transit, aerospace and machinery manufacturing. The ceramic phase Mo₂C was added to the copper/graphite composite to form a three-phase synergistic reinforced composite, thus effectively solving the problems of low density and poor electrical conductivity caused by the poor wetting property of copper and graphite. In this paper, the influence of the size and volume fraction of Mo₂C grains on the infiltration behavior of copper melt and the porosity formation of the composites were systematically studied by using two-phase flow finite element model. The results show that the addition of a small amount of Mo₂C can promote the effective transfer of displacement pressure and reduce the capillary resistance of copper melt in graphite matrix. When 0.03% Mo₂C with particle size of 1μm was added to the graphite matrix, the porosity of the three-phase synergistic reinforced composites decreased from 44.35% before infiltration to 2.28%. Compared with the copper/graphite system, the conductivity and densification rate were increased by 16.98% and 25.83% respectively. The results provide a new solution for the development of copper/graphite composites with high electrical conductivity.