Abstract: Based on the existing research achievements and the authors’ recent work, the chemical modified soils are classified into five categories i.e. inorganic soils, organic soils, inorganic-organic compound soils, chemico-physical soils and polluted soils. The definitions of the five categories of chemical modified soils are presented, and their origins, engineering properties, mechanisms, applications, advantages and disadvantages are also analyzed and summarized in this paper. The research indicates that the five chemical modified soils have different engineering properties, formation mechanisms and engineering applications; The effect of modified soils depends on the modified material properties, soil properties and modifying technology. The chemicophysical soils are the best one in improving the engineering property, while the polluted soils can only be used after an effective treatment because in general their engineering properties and environmental effect can not meet the engineering requirement. The chemically modified soils have wide application prospect in the field of environmental geotechnical engineering.