Spheroidization of primary α-Al phase in semi-solid A356 aluminum alloy slurry prepared by a serpentine channel was observed.The results show that amounts of fine gain-free and dendrite can be created in the under-cooling alloy melt in serpentine channel as a result of chilling effects of inner-wall,in which the majority is drifted to the central zone of serpentine channel and multiplied,and then parts of are evolved into spherical grains and dendrite by spheroidization and ripening,and other parts are grown into dendrite with large size,