The invention discloses an expansive soil discrimination and classification method based on physical and chemical characteristics. The method includes the following steps that firstly, soil samples are detected, wherein the soil samples are collected, and chemical indexes of the pH value, the specific surface area, the Zeta potential, the cation exchange capacity and the conductivity in the soil samples are measured; secondly, SPSS software is used for performing Fisher discriminant analysis on the collected soil samples, discriminant analysis is performed with the chemical indexes of the pH, the specific surface area, the Zeta potential, the cation exchange capacity and the conductivity of the soil samples as discriminant analysis variables, and discrimination and classification functions relate to high expansive soil, middle expansion soil, weak expansive soil and non-expansive soil respectively; thirdly, due to discriminant analysis in the second step, the categories of the soil samples are determined, and the soil samples are classified into the high expansive soil, the middle expansion soil, the weak expansive soil and the non-expansive soil respectively. The classification method can be used for fast discriminating and classifying expansion soil, needed experiment raw materials are few, the measurement result is accurate, and the method has good application prospects.