In this study, the volume change of soils is assumed to consist of two components, consolidation and contractancy (negative dilatancy). The authors develop two categories of elasto-plastic constitutive model by employing two types of non-linear function capable of describing contractancy (negative dilatancy) of soils in a wide variety. Proposed functions have a good capacity for describing experimental data. The well-known constitutive models for soils, such as the Original Cam-Clay model, the Modified Cam-Clay model, the Ohta-Hata model and the Sekiguchi-Ohta model are included in the obtained group of models.