The laser-desorption-ionization time-of-flight mass spectro metry and desorptionelectron-ionization mass spectrometry were employed for the characterization of metallofullerenes extract. It was found that the relative intensities of metallofullerenes in this positive-ion, negativeion LD-TOF MS and DEI MS were much different. This phenomenon should have relationship with the peculiar ionization energies and electron affinities of metallofullerenes.