Abstract: The mass spectrometric analysis of germanium isotope by a boat-filament ion source, adding silica-gel mixture to germanium dioxide to enhance the measurable ion beam, is reported. The methods of correcting the germanium isotopic ratios for the mass fractionation and electron multiplier discrimination are described in detail. The results of natural germanium isotopic abundances are ~(70)Ge = 20.50%, ~(72)Ge = 27.48%, ~(73)Ge = 7.76%, ~(74)Ge = 36.51%, and ~(76)Ge= 7.75%, respectively.