Abstract: Microwave-assisted sample digestion was used for the pretreatment of the oil samples.Parameters of sample quantity,amount of acids,digestion time,microwave power and digestion program were optimized.And flame atomic absorption spectrometry was used for the determination of Fe,Ni,Cu in crude oil and residual oil.The method had the advantage of less loss of sample,less consumption of reagents,reduction of environmental contamination,and the analysis period was reduced by 3.5 fold as compared with the dry-ashing pretreatment.Results of determination were in agreement with those obtained by the routine method.Relative errors were 1.6% for Fe,1.4% for Ni and 1.6% for Cu,respectively.It is a green analytical method of analysis favourable to environmental protection.