This paper introduces a new method which can obtain the extinction value linear to the concentration for the atomic absorption spectrometry (AAS) and atomic resonant fluorescent spectrometry (ARFS). The modeling experimental results exhibit that the measurement sensitivity is increased obviously too with this method. When the ARFS instead of AAS is used, not only the expression covention of the measure in extinction value is retained and there are also the property which the continuous radiant source and the lower resolution, monochromator applicable in ARFS, thus this unify processing method of extinction data exhibits some potential superiority.