In order to elucidate the extrusion characteristics of $SiC_{p}$/6061 Al composite, defomation resistance, $K_{w}$ was determined using the empirical formula suggested by Watanabe et al, and also extrusion pressure was measured using the extrusion press with a capacity of 350 ton. The $K_{w}$ which are propotional to extrudability, was increased with increasing volume fraction of reinforcement, $SiC_{p}$, but decreased with increasing the particle size. The peaks of maximum extrusion pressure in curves of extrusion force vs ram stroke were changed sharply with decreasing the particle size. The elevated extrustion temperature resulted in the decreased $K_{w}$ and extrusion pressure, but caused the surface tearing of extrusion composite bars. The results showed that extrudability of the composite billets is depend on the extrusion conditions as well as the characteristics of reinforcement, $SiC_{p}$.