In this paper we put forword a constitutive model based on thermodynamics,Byintroducing generalized time scale, unified constitutive equation including descoription of creep,plasticity and the creep-plasticity interaction effects, is presented,It is shown that the present unifiedconstitutive equation includes plasticity as one special case(dt=0)and creep as the other one(ds=0).By means of analysis of material subetructure for creep, plasticity and creep-plasticityinteraction,a multiplicative harderung function analysis developed here has been compared with Ohashi'sexperimental results,It seem that the present theory could satisfactorily describe Ohashi'sexperimental results.