Abstract: Pipeline transportation is the most important part of CCUS technology while the high concentration of suffocating carbon dioxide leakage and a small amount of toxic gas impurities are the most important potential hazards, so safety is an important consideration. In this paper, the leakage and diffusion of carbon dioxide and its impurity hydrogen sulfide were simulated and analyzed by using the PHAST software, leading to the simulation of the most dangerous conditions. And through the simulation and analysis of the dangerous conditions on the carbon dioxide pipeline transportation, the maximum safety distance of carbon dioxide and hydrogen sulfide gas diffusion were determined, and the appropriate stop valve spacing was selected. Quantitative analysis and evaluation of the safety of carbon dioxide pipeline transportation was conducted, which can be used as reference for the future development of carbon dioxide pipeline standards.