In this work, the relationship between the theoretical atomization efficiencies (EA') and atomization temperature (T) in graphite furnace atomic absorption spectrometry (GFAAS) for 18 elements were studied in detail. The results showed that a linear relationship between the EA' and the atomization temperature existed at a definite atomization temperature range. The correlation coefficient was within 0.9940-0.9993 for 18 elements. The slope was in the range of 0.06-0.07. The theoretical atomization efficiency was about 65% for all elements at optimized atomization temperature. This indicated that some factors should be taken into account in the L'vov modified model of characteristic mass.