Abstract: The processes of the deformation,the crack initiation and growth in SiCw/Al composite have been observed by means of the in-situ transmission electron microscopy straining techniques.The results indicate that a great deal of dislocations would arise around grain boundaries and whiskers in the early deformation stages.Cracks are initiated mainly in whisker-riched regions and by the crack of the whiskers injured during the preparation for the composite.The whiskers and grain boundaries in the composite play an important role in impeding the crack growth.When the whisker in front of a crack tip is perpendicular to the crack,the crack tip would blunt near the whisker side and then advance along its nearinterface-region.Under the condition of the whisker in front of a crack tip parallel to the crack,the crack tip would blunt near the whisker end and then propagate along the nearinterface-region.