Rapidly solidified high silicon aluminum alloy powders were prepared by ultrasonic gas ato mization process. Phase constituent, microstructure characteristics, micro-hard ness of the alloy and influence of ageing treatment were studied systematically . The results showed that the microstructure of high silicon aluminu m alloy powders prepared by ultrasonic gas atomization process mainly consists o f fine particle Si phase distributed dispersedly in matrix and needle-like Al 9FeSi 3 phase. The diffraction peaks of the matrix and Si phase were broaden in a certain extent in the XRD diagram. The microstructure and phase constituent o f the alloy powder by ageing treatment are almost unchanged but the diffraction peak width is narrowed slightly. The micro-hardness of the alloy powder decreas ed somewhat in the initial stage of the ageing following unchanged with the pro longing of the ageing time.