Mr. Chen Huanming’s team investigated the micro-structure characteristics of a kind of superallowy powders (similar to Rene 95) prepared by plasma rotating electrode processing (PREP) by using SEM and calculated the relation between cooling rate and particle size distribution. The results indicate that the solidification micro-structure of particle surface are dendrite and cellular structures. With decreasing of particle size, the particle interior micro-structures change from dendrite in major to cellular and micro-crystal structures. This has important guiding significance for producing high-quality metal powders using the PREP method.