Classification of the shrink and expansion grades of expansive soils is an initial and essential work for engineering construction in expansive soil area. Based on the engineering methods of Extenics theory, five indexes, including free expansion rate, swell-shrink total ratio, the liquid limit, plastic index, and clay particles of less than 0.005 mm are selected as the factors for comprehensive  evaluation of expansive soil. To avoid the impact of subjectivity on weights allocation in traditional method of extenics evaluation index, the entropy theory is employed to calculate the weight aggregation of evaluating factors. An extenics model based on entropy weight is established and applied to the classification of expansive soil samples collected from Xiangyang-Jingzhou expressway. It is shown that the entropy matter-element model is highly reliable and easy-to-operate. The classification results are rational and objectively reflect the complexity of judging the shrink and expansion grades of expansive soils.