The aim of the present work is to study the effect of semi-solid processing using cooling slope method on the microstructure and mechanical properties of grey cast iron. A water cooled castable cement coated steel plate with a variable inclination angle is used to make a mechanical treatment on the semi-solid flow of grey cast iron. The experiment is repeated for three different pouring temperatures and three inclination angles. The tensile test, hardness test and microstructure examination is used to compare the new properties of the new resulting grey cast irons. The results show that the sharp-edged carbon flakes can be refined and the mechanical properties is enhanced. The carbon particles average circularity is increased followed with a decrease in carbon particle size due to the effect of the cooling plate.