The Casting technique of fabricating SiCp/ZA27 by mechanical stirring of semi solid slurry and the effects of SiCp content and size on tensile and hardness of the composites have been discussed. The fracture surfaces of the composites have been examined by SEM. The results indicate that SiCp/ZA27 with uniform distribution of SiCp can be obtained. The tensile strength decreases with the increasing of SiCp content and size. The apprearance of fracture is characterized by partial dimples

and formation mechanism is different with variance in SiCp content and size. The hardness of composites increases with the increasing of SiCp content V （SiCp）<5%

while it decreases at SiCp content V （SiCp）>5%. The hardness of composites reinfored by finer SiCp is higher than that of composites reinfored by coarser.