Abstract: There exists a nonlinear cohesive zone at the crack tip in stretching hydroxyl terminated polybutadiene (HTPB) propellant, and the accuracy of its constitutive model can affect the fracture simulation greatly. In order to establish a precise constitutive model, an experiment-based inversion method was presented. The cohesive fracture energy and fracture strength were obtained experimentally, and the constitutive curve parameters of cohesive zone were determined by using the finite element model updating approach. The established constitutive model was applied to the crack initiation and propagation simulation. The results indicate that the presented method is simple and feasible, and it can predicate the crack initiation and propagation in HTPB propellant accurately.