Abstract: The superplastic mechanical behavior and deformation mechanism of the beta-SiC whisker reinforced 2024 aluminum composite, fabricated by low-pressure infiltration and hot-rolling after extrusion with a low extrusion ratio of 10∶1, were investigated by using elevated tensile tests, transmission electron microscopy, X-ray diffractometer, differential scanning calorimeter and the conventional theory of superplastic deformation mechanism for fine grain metals. The results show that the composite has a fine grain size of about 1 μm, and exhibits a maximum tensile elongation of 370 % in the initial strain rate of 3.3×10^-3s^-1 at 788 K. A small incipient melting peak on DSC curve of the composite appears and corresponds to the peritectic reaction of Al+CuAl₂+Cu₄Mg₅Si₄Al x→Liquid+Mg₂Si at 785 K. The superplastic deformation mechanism of the composite is grain boundary (interface) sliding controlled by grain boundary diffusion of the aluminum atom and an appropriate amount of liquid phase.