Abstract: Cu-Ni alloy powders were synthesized by ultrasonic assisted electrical discharge machining (EDM) method with copper and nickel metals as positive and negative electrodes, respectively. The effects of ultrasonic power (0, 500, 1 000, 1 500 W) on the crystal structure, micromorphology and particle size distribution of the alloy powder were investigated. The results show that the phases of Cu-Ni alloy powders synthesized by ultrasonic assisted EDM under different power conditions were all composed of Cu_0.81Ni_0.19, Ni, CuO, NiO and Fe₂O₃. The main crystal phase Cu_0.81Ni_0.19 had a face-centered cubic structure. With increasing ultrasonic power, the diffraction peak intensity of the Cu_0.81Ni_0.19 increased while the full width at half maximum became narrower, indicating the better crystallinity of the powder. Irregular particles with large size appeared in Cu-Ni alloy powders synthesized by the ultrasonic assisted method, but the size of spherical particles decreased and the distribution range of particle size became wider. With increasing ultrasonic power, the average particle size D₅₀ decreased.