Abstract: Tne fatigue crack initiation sides,initiation life and mechanisms are studied in a SiCw/LD2 composite.The fatigue microcracks near the ends of whiskers and dislocations in the matrix are observed by TEM.The surface replicas taken from the specimen surfaces duriy fatigue, are examind by SEM, and a 5 micrometer long fatigue crack is found. It is considered that the fine grains can prolong the initiation of fatigue microcracks in the composite,which is one of the reasons leading to the higher fatigur strength of the composite.