The present work encompasses the development of a new method of cooling plate casting process by changing the inlet and outlet of water flow which is different from the conventional cooling plate casting process. This process consists in pouring the molten metal at temperature close to the liquid line in an inclined cooling plate. Pouring temperature and inclination angles have effect on microstructure. The following variables have been used in this work: pouring temperatures of (750, 800. and 850 ᵒ C), tilt angles of (30 ᵒ , 40 ᵒ , 50 ᵒ , and 60 ᵒ ), and Mg additive of (1%, 5%) with constant cooling length (380mm). After the melt flow down cooling plate, the melt becomes a semi-solid slurry at the end of the plate. Optical microstructure test shows that, the pouring temperature and tilt angle affect the size. Grains shape decreases with decreasing of tilt angles and with decrease pouring temperature as well as Mg addition also has the same effect on Al-Mg microstructure. X-Ray diffractography for Al-Mg alloys shows the appearance of peaks of intermetalic compound and different phases of (Al 3 Mg 2 , Al, δAl 2 O 3 )and for Al-1%Mg has a phases (Al Mg , ,MgO ),while SEM picture shows , Al 3 Mg 2 phase as dark region and α-Al as light region for Al-5%Mg, and Al Mg phase for Al-1%Mg.