Abstract: The microstructure characteristics of interface in δ-Al₂O₃ short fiber reinforced Al-5.5Mg alloy composite at different temperatures were observed by TEM. In the meantime, based on the single fiber model of the short fiber reinforced metal matrix composite, the thermal residual stress states of interface were calculated by an elasto-plastic finite element method. The effects of the interfacial thermal residual stress on the mechanical behavior of interface at various temperatures were also discussed. At last, the effects of varied microstructure features and thermal residual stress states of interface on the whole mechanical behavior of the composite were analyzed. It is shown that the microstructure features and thermal residual stress states of interface change with the variation of ambient temperatures, which then results in the different mechanical behavior of the composite.