Abstract: The influences of content of cerium on the transition of various forms of graphites in casting iron is studied by means of undirectional solidification, optical microscope and scanning electron microscope. The conclusions are that, as the content of cerium is increased gradually, the flake graphite can transformed successively to supercooled graphite, vermicular graphite, intcrdendrile vermicular graphite and sector-like graphite under a constant moving speed of interface between solid and liquid. According to the results of referencc﹝1﹞ the conclusion is drawn that the morphology transition between nodular graphite, vermicular graphite and flake graphite is reversible. Besides, the coupling eulcctic growth between graphite and austcnilc is observed even in a liquid of high content of cerium.