Mechanical properties of elastomeric composites in particular carbon black filled rubbers considerably depend on uniformity of distribution of filler and sizes of its clusters in an end-product, i.e. from quality of mixing of a composite compounds. In present work the technique of the quantitative analysis of structure of the filled rubber by atomic-force microscope (AFM) is elaborated. The analysis of images depending on height over zero level of a relief has shown that the number of clusters, their area and compactness.