Abstract: Conventional (room temperature) and warm (200 ℃) shot peening treatments were performed on Al₁₈B₄O₃₃ whisker reinforced aluminum matrix composite, and the residual stress distribution of the surface layer after shot peening was studied. The microstructure of the surface layer was investigated by X-ray diffraction profile analysis and the microhardness was also studied. The results show that the residual compressive stress of the surface layer of the composite after shot peening increased first and then decreased with increasing distance from the surface (depth); the residual compressive stress after warm shot peening was greater than that after conventional shot peening. The domain size of the surface layer increased with the depth after shot peening, and the microstrain decreased; the domain size and microstrain after warm peening were both smaller than those after conventional shot peening. The dislocation density and microhardness of the surface layer decreased with increasing depth after shot peening, and the dislocation density and the microhardness after warm peening were higher than those after conventional shot peening.