Abstract: To solve the problem that the existing fluid-solid coupling structure model cannot be widely applied for predicting crack propagation in CO₂ pipelines due to its high difficulty in modeling and low computational efficiency, the paper proposes a simulation method for the dynamic crack propagation of supercritical CO₂ pipeline based on a decompression model. In this method, the complex fluid-structure interaction between pipeline fracture and fluid release is achieved by a three-dimensional CO₂ pressure decompression model combined with loading subroutines, which is first proposed based on pipeline pressure data obtained from full-scale burst experiments and numerical simulations. The coupling relationship between pipeline and soil under large deformation is described using the smoothed particle hydrodynamics (SPH)method. To verify the reliability of the proposed numerical simulation method, it is used to reproduce the pipeline burst tests; based on this method, a comparative study is conducted on the ductile fracture behavior of CO₂ pipelines without backfill, with half and full backfill. The results indicate that the proposed method is reliable. The error between the simulated and experimental values of crack propagation speed under two working conditions is 21.6 % and 7.6 %, respectively, demonstrating that the established decompression model can effectively describe the space-time evolution of the pressure in the CO₂ pipeline during crack propagation and can avoid solving complex fluid structure coupling problems, thus laying the foundation for the subsequent parameterization study of fracture behavior and the construction of crack arrest prediction models for supercritical CO₂ pipelines. The research result also shows that soil backfilling has a significant influence on crack propagation length, velocity and whole deformation of pipelines. Compared with pipelines without backfill, the crack velocity of fully backfilled pipelines is decreased by 19 m/s, and the pipeline deformation is significantly limited, which is beneficial for crack arrest.