Algorithm of magnetic structure extraction and analysis in ultra thin magnetic film images is proposed. This algorithm allows to gain successful results and calculates a large number of characteristics of structures on magneto-optical images. The algorithm consists of three parts: background correction, structure extraction and calculation of dendrite characteristics. For correction of magnetic image we use methods for magneto-optic contrast. One of the basic features of structure extraction part is a preservation of border properties. Therefore the basic processing of extraction is applied for binary image. Proposed characteristics allow to describe and to classify dendrites. For analysis of complex magnetics structures topological properties are calculated for three basic objects types: body, holes and gulf. The software system “Zubr” has been realized for magnetic structure image analysis.