Abstract: By selecting modifiers and optimizing various experimental conditions, a direct determination method of arsenic contents in crude oils and heavy oils by graphite furnace atomic absorption spectrometry (GF-AAS) is established. The linear range of this method is arsenic mass fraction in the range of 16—3 000 μg/kg with detection limit of about 5.4 μg/kg, the relative standard deviations of reproducibility tests are less than 10% and recovery rates of standard addition are more than 90%. In conclusion, this method has the advantages of fast determination, high sensitivity and easy to be operated, which can well meet the demand of routine analysis.