The elastoplastic constitutive relation of high compressibility clay in Wuhan was investigated. On the basis of the framework of Duncan E~v model, an elastoplastic constitutive model was derived by fitting the data of triaxial compression tests under CTC stress path on isotropic consolidation condition. With the average slope of unloadreload curves as unload modulus, the loadingunloading function was introduced as the loadingunloading criterion. Moreover, the comparison was made among the stressstrain relation curve simulated by the proposed model and those with Duncan model and test curve. It was shown that the proposed model was more reasonable, which can reflect the stressstrain relation of normally consolidated soils under CTC path. Especially, the model can reflect the strain strengthening effect. The maximum relative error was no more than 5%.