A new preparation technology, termed powder semi-solid (PSS) casting, has been developed for the preparation of fine-grained alloys. In this process, certain amount of alloy powder, which has the same composition as the melt, is added into the melt and then immediately stirred until the powder is uniformly distributed. The M7C3 carbide phases in the as-cast alloy are fine batten-like or in equiaxed shape and their ratio of length to radial reduces. The eutectic colonies are refined greatly comparing with that of the conventionally cast alloys, and their size are between 20 and 50 μm. The α-Fe transferred from primarily precipitated austenite is refined too. Furthermore, the PSS casting technology can also modify the morphology of austenite grains and refine them effectively.