A data processing combination of manual and automatic steps for mass peaks identification of a coking gas oil was illustrated.Some representative compounds were identified by manual process.A program was performed to search the various types with the same hetero-atoms(familes-class,NnSsOo)but different rings plus double bonds(R+DB)value(Z in CcH2c+ZNnOoSs),then,alkylation series of each types were revealed by multiplying each mass by 14.00000 in Kendrick mass scale.Finally,isotope groups of each identified peaks were picked up respectively.The method is appropriate to the data analysis of FT-ICR MS spectra with a poor mass accuracy.