We study the interface shock viscosity in the Hydroxyl-terminated polybutadiene (HTPB)-Ammonium Perchlorate (AP) based energetic material. A strain rate dependent power law viscoplastic stress-strain model was used as the constitutive behavior of interface, particle, and matrix obtained from dynamic impact experiment. A tensile fracture experiment combined with an In-situ mechanical Raman Spectroscopy is used to obtain cohesive zone model. The cohesive zone parameters and the viscoplastic model obtained from the experiment were then used in the cohesive finite element method to simulate the shock in one particle HTPB-AP sample. Interface Shock viscosity were obtained from the Cohesive Finite Element simulation results as a function of strain rate. Interface shock pressure is shown to have a power law dependence on the strain rate. Interface shock viscosity is shown to increase linearly with respect to the strain rate. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.