Sketch-based military marking diagrams consist of many linear and regional symbols. Typically, these symbols are irregularly shaped because they are drawn according to specific terrain or battle scenario with freehand. Therefore, they are also called irregular symbols. Traditional appearance-based methods are not appropriate for recognizing these symbols. A structural recognition method for sketched irregular military marking symbols was proposed. Symbols were decomposed and represented by 9 types of primitives together with 4 types of spatial relationships among them. By matching the primitive counting vector and the primitive relationship matrix of the unknown symbol with those of the templates, the class label was recognized, and their primitive correspondences were also estimated. Experimental results demonstrate that the proposed method is effective and efficient for recognizing sketched irregular military marking symbols.