Pure carbon, pure iron and single crystall silicon were firstly loaded into a pure graphite crucible to obtain a hypereutectic Fe-C melt by carburizing at high temperatures in this paper. The powder of oxide La2O3 and CeO2 were added respectively to the melt under the same process conditions and cast iron samples were obtained. The graphite morphology of the samples was observed under optical microscope and SEM. Matrix of the samples were etched by electrolysis way. At last non-ferrous residue on the surface of cast iron samples was gathered, calcined,observed under SEI and BEI and analysed with EDS to find the trace of oxide La2O3 or CeO2. The results showed that oxide La2O3 or CeO2 was really added into the melt but the morphology of graphite did not change. The only effect of the oxides was making the amount of graphiteto increase slightly. All the results of this paper indicat that the oxide La2O3 or CeO2 is possibly the base for graphite flake to precipitate but is not a sufficient condition for graphite to nodularize.