Structure has a major influence on the stressstrain relation of soil, which implies that the constitutive model should reflect the its structure. Based on the investigation , the overconsolidation (OC) of the soils was made up of two different types, which were structureinduced OC and stressinduced OC. And then the structureinduced OC and stressinduced OC were united. Structureinduced OC index was used to represent the degree of structure and the cam clay model was extended. The shape of the yield surface was the same as cam clay model, whise the size was equal to the sum of the structureinduced OC and stressinduced OC. And the change in size of the yield surface was decerminated by the volumeharden function and the structural damage function. The associated flow rule was adopted in the model. Afterwards constitutive model for structured clays was presented. The concept of the model is clear and the parameters are simple. The ability of the model is good by firstly application and it can describe the character of the structured soils.