Semi solid casting has been studied and used as one of the rather new ways of manufacturing metallic parts due to its advantages over other common casting processes. The majority of the studies were on low melting point alloys and ferrous and high melting point alloys have attracted less attention. In the present study, the microstructure and properties of a SSR cast hypereutectic gray cast iron was evaluated. SSR is a semi solid casting process based on local cooling of the liquid phase and producing and dispersing nuclei into it. Presence of a lot of large Kish graphites in the microstructure of a hypereutectic gray cast iron results in low mechanical properties. Hypereutectic gray cast irons have remarkable physical properties such as high heat transfer ability and high trembling absorption ability, so in case of better microstructure and mechanical properties they could make more efficient metallic products. In this research first the ingot with distinguishing composition was made and after melting and SSR treatment of the alloy, it was poured into two sandy and metallic molds and pressed by squeezing. As the next step, micro and nano size inoculants were added to the liquid phase for casting. Then theeffect of different treatments on microstructures, physical and mechanical properties were evaluated. The results showed that semi solid casting of a hypereutectic gray cast iron changed the dendritic microstructure to spherical, made the graphites smaller, removed Kish graphites and produced D type graphites. The microstructures underwent more changes in the cases of metallic mold, pressing and adding inoculants.The effect of two types nano size and micro size inoculant wasn’t very different on mechanical properties and microstructure. SSR treatment resulted in higher densities of the samples and the squeezing was also effective so that the density increased from 7.05gram per cubic centimetre for the sand cast refrence sample to 7.4gram per cubic centimetrefor the squeezed one. The microstructural changes improved the electrical resistivity from 3.9×10 -4 ohm centimeterfor the sand cast reference sample to 1.47×10 -4 ohm centimeter for the SSR treated and squeezed one. Based on mechanical tests, the improvement in microstructure and graphite morphology resulted in higher tensile strength, bending strength, hardness and wear resistance. The tensile and bending strength increased from 116.3MPa for the sand cast reference sample to 168.9MPa for the SSR treated with addition of nano size inoculant and from 254.9MPafor the sand cast reference sample to 424.7MPa for the SSR treated with addition of nano size inoculant respectively for the SSR treated sample containing nano size inoculants. SSR treated and squeezed sample had the highest hardness and it was 215.6HV. It referred to its high density and also the structure and morphology of the graphites. The under pressure solidified sample had the highest wear resistivity. Larger Kish graphites and lower D type grapites resulted in better lubrication and higher wear resistance of reference samples. Key words Semi solid casting, SSR method, Hypereutectic gray cast iron, Nanosize inoculant, Mechanical properties.