Abstract: The “second coke” was prepared by mixing binder pitch with pitch coke followed by carbonization at elevated pressure. The carbon/graphite composites were prepared by using this powdered “second coke” as filler and coal-tar pitch as binder. The effect of the average particle size of the “second coke” on the mechanical strength, shrinkage behavior and open porosity of the composites was studied. Results showed that the composites had high mechanical strength. The compressive and flexural strengths after heat-treatment at 1300℃ were 310.0 and 113.7MPa respectively. The influence of the average particle size on the mechanical strength was remarkable when the heat-treatment temperature was under 1300℃. The volumetric shrinkage of the composites was decreased by decreasing the average particle size of the filler. The open porosity of the composites exhibited a maximum at 850℃.