The processing of metals in the semi-solid state is becoming an innovative technology for the production of globular structure with minimum microsegregation and high quality cast parts. This research is aimed to study the microstructure characterization andmicro-segregation of semi-solid processing gray cast iron. Increasing fraction of solid has significant effect on the primary particle morphology as well as micro-segregation of gray iron cast structure. Elements segregation decreases with increasing the fraction of solid up to 0.12. It is found that elements segregation starts to increase by increasing fraction of solid above 0.12. This change of behavior of elements segregation before and after 0.12 fraction of solid related to primary solid agglomeration. Processing window (fs = 0.02 to fs = 0.13) can be withdrawn for production of semi-solid gray cast iron casting combine higher strength, higher elongation and minimummicro-segregation compared with ordinary gray iron casting.