The existence of viscosity effect at the interface of double dissimilar materials has an important impact to the distribution of interface crack-tip field and the properties variety of the interface itself. The singular is considered in crack-tip, and the elastic-viscoplastic governing equations of double dissimilar materials at quasi-static propagating interface crack-tip field are established. The displacement potential function and boundary condition of interface crack-tip are introduced, and the numerical analysis of rigid-elastic viscoplastic interface for mode II are worked out. The stress-strain fields are obtained at the crack-tip and the variations of solutions are discussed according to each parameter. The numerical results show that the viscosity effect is a main factor of interface propagating crack-tip field, and the interface crack-tip is a viscoplastic field that is governed by viscosity coefficient、Mach number and singular factor.