The basic types of graphite morphology in nodular cast iron is introduced. According to the graphite morphological features, matter-element analysis theory is applied to establish the matter-element model for graphite morphology recognition. In this paper, extension classification tree is proposed. The way of construction and realization of extension classification tree is given. Extension classification tree is used to identify the graphite morphology. The typical experiment results are given. The method is compared with other current recognition methods.