Abstract: There are many extinction characterization methods for soot, but they always cost much when used to appraise the extinction characteristics of soot with unsteady distribution. This paper introduces a simple extinction characterization method. It appraises the extinction characteristics of the soot with its mean mass extinction coefficient weighted with the mass concentration. According to the theory derivation, the extinction coefficient of the soot is the product of the mean mass extinction coefficient and the total mass concentration. Fortunately, every term in the expression of mean mass extinction coefficient can be obtained by theoretical and experimental methods. A theoretical analysis of variance tendency of mean mass extinction coefficient is carried out associated with the variance of diameters and aggregate sizes of the soot. It predicts that the mean mass extinction coefficient decreases significantly at first with the decrease of the diameters and aggregate sizes of the soot, and then slightly since it enters into the glacis.