Compacted graphite was obtained using inmold technology. The effect of aluminium on the crystallization process, microstructure, ferrite microhardness, and hardness of compacted graphite iron was studied. The microscopic and diffraction tests were also performed, and the process of cast iron crystallization was also investigated. Results show that aluminium increases the temperature of the eutectic transformation as well as the transformation temperature in the solid state. It is found that aluminium is a graphite forming element in compacted graphite iron (CGI) at a concentration up to 2.4wt.％. When its concentration is higher than 3.1wt.％, aluminium causes the spheroidization of the carbides in eutectoid mixture. It is also demonstrated that in cast iron with an aluminium content higher than ～8wt.％, AlFe3C0.5 phase crystallizes from the liquid.