Abstract: Due to the layer-by-layer compaction effect in dam construction, the static and dynamic shear strength of RCC (Roller Compacted Concrete) layer is less than its body strength. Discontinuous deformation and dynamic slip instability may occur along the RCC interface (including foundation interface) under the action such as earthquake, vibration or shock effect. Based on the Perzyna’s viscoplasticity constitutive theory, a dynamic shear constitutive model is presented in which the shear fracture behavior of RCC interface can be described. Characteristics of the model proposed herein are: plastic softening and dilatancy behavior are directly related to the fracture process of interface; improved rate-dependent interface model by Carol is used as yield function to capture the strain effect of RCC; the process of decohesion coupled with frictional sliding is described by classic plastic-fracture mechanics and much less material and model parameters are required. The proposed model is applicable to dynamic strength experiments of RCC containing interface with different loading path including uniaxial tension and compression, compression-shear under various loading rates. The result shows, the proposed elastic-viscoplastic dynamic shear constitutive model can describe the failure processes and mechanisms of RCC structures with weak layers effectively, and can be a suitable numerical tool for the related practical engineering.