Macro and micro structures by optical microscope(OM), scanning electro microscope(SEM) and transmission electro microscope(TEM) of AC4A/SiCw 10-30v/o reinforced composites were observed. Fracture mode of AC4A alloy was appeared to be plastic. But fracture mode of composites were appeared to be almost elastic. And that was occured very well with increasing of SiC whisker volume fraction. Mechanical characteristics of preformed SiC whisker reinforced composites by squeeze casting technique were more affected by squeezing pressure than temperature of molten metal. Distribution of dislocations at matrix of composites was uniform. But the number of dislocations around whisker of composites was much more than in matrix. These diffraction pattern were [011] direction for both matrix and around whisker.