Mechanism of fullerene formation has been argued for many years for lack of reliable intermediates.Although many possible intermediates have been captured through introducing new reactants into Kr1itschmner-Huffman process, the relationship between trapped compounds and fullerene formation is still unclear.Herein we proposed a 13C-marked method to trace fullerene growth.A 13C abundance gradient was built via two different 13C-containging carbon sources (graphite and CCl4) used in the graphite arc-discharge with CCl4 in helium atmosphere.This 13C-marked experiment coupling with kinetics simulation is able to locate the objective products in the reactor, to decide the reaction temperature, and to distinguish the intermediates from the other byproducts, by means of the comparable isotopic distribution in the recorded mass spectra.A reasonable pathway for fullerene formation is suggested via the special connections among fullerene fragments, smaller fullerenes, C60 isomers and conventional fullerenes.