PURPOSE: To provide a producing method for an Al alloy base partial strengthened piston improving the wettability between an insert material and matrix at the initial stage and excellent in the wear resistance and the thermal conductivity with light wt. and at a low cost.

CONSTITUTION: The surface roughness Rmax of the insert material 5 is made to 0.01-0.1 to improve the wettability at the solid-liquid coexistent temp. or an interface between molten metal and the insert material. Then, as the insert material 5, the composite raw material composed of a forged product of high Si-Al alloy or rapid solidified Al alloy powder or Al alloy as the matrix and metallic or ceramic fibers or powder as a reinforcing material, is used.