A novel mechanochemistry approach, defined as solid-liquid reaction ball milling, was applied to obtain single-phase Al-Cu-X (X = Fe, Co, and Ni) ternary intermetallic compound powders by reactions between milling medium (ball and cylinder) and liquid-state metals in certain temperature range, where the milling mediums made of metals with high-melting point and took part in the reaction as the solid-state reactants. Compared with the conventional mechanical milling technique, nanometer-sized intermetallic compound powders and some single-phase ternary intermetallic phases could be obtained at lower temperatures by the solid-state reaction ball milling. Furthermore, the reaction mechanisms of this mechanochemical approach have been discussed in details.