Abstract: A numerical analysis method is developed to solve the problem of crack propagation in gas pipelines. It is based on the fundamental theories, methods and arrest criteria in dynamic fracture mechanics as well as finite element method (FEM) in shell dynamics. For high toughness pipelines, the decrease of heat dissipation caused by plastic work unloading cannot be neglected. By referring to the energy balance equation under the condition of nonuniform crack propagation, an iterative method is constructed to solve the instant speed in FEM. The dynamic fracture toughness comprised mainly of the heat dissipation rate is obtained through experiments, and is used as the given function of crack speed, to replace the original steady propagation mode and form the toughness-induced deceleration mechanism. To determine the parameters required in calculation, the two-specimen DWTT method is deducted to determine the heat dissipation rate formula.