Hydrogen-doped natural gas pipelines is affected by hydrogen damage and other factors,which is easy to produce defects and lead to pipeline failure,so it is necessary to check the hydrogen-doped pipeline regularly.The main defects generation mechanism and defect characteristics of hydrogen-doped pipelines were analyzed,and the main defect forms were summarized.An external magnetic flux leakage detection mechanism was designed for hydrogen damage in hydrogen-doped pipelines to detect defects in pipelines,and Maxwell software was used to simulate magnetic flux leakage detection.The function between the parameters of the detection probe and the peak-valley difference of the axial magnetic leakage curve,adsorption force and cost was established by the response surface method to optimize the probe structure parameters.At last,an experimental platform was set up and a single probe was used to detect the magnetic flux leakage in a single channel.The results show that compared with the non-optimized structure,the detection effect for defects outside the pipelines is increased by 26.2%,and the detection effect for defects inside the pipeline is increased by 11%,the adsorption force between probe and pipeline wall is reduced by 56.7%,the probe cost is reduced by 14%,so the detection effect is improved after the optimization.The optimized probe can not only detect defects in formed and more obvious hydrogen-doped pipes,but also detect defects when the wall loss reaches 40% of the overall wall thickness in the early stages of defect formation.The feasibility of the design scheme is tested by defect detection.