Abstract: A Mechanism of the G.S structure consisted of comical helixes is presented based on TEM, and the arrays of misoriented graphite platelets 0001 in each comical helix are believed to be grew up in spiral. The effects of Mg and Ce additions on the nucleations and growth of graphite are also discussed. The microstructure on the section of G.S observed earlier can be explained satisfactorily in term of the model.