A simple and effective method to add large amounts of expanded graphite (EG) to poly (phenylene sulfide) (PPS) was developed. Before conventional melt processing, solid-state PPS and EG powders were mixed using high-speed rotation. In this way, the loose and porous vermicular structure of EG could be effectively destroyed and partly exfoliated, which made EG easy to be adsorbed on the surface of the PPS powders. This was extraordinarily helpful to achieve good dispersions of EG during the subsequent melt mixing even at high loading, which was difficult to achieve by conventional direct melt mixing. As a result of the good dispersions and strong interactions, the EG/PPS composites prepared showed a dramatically improved thermal conductivity (15.8 Wm(-1)K(-1)) and electrical conductivity (125.3 Sm-1) as the addition of EG reached 60 wt%.