In order to quickly define the dangerous distance of leakage in hydrogen?blended natural gas high?pressure pipelines, this study established a mathematical model of small hole jet leakage of hydrogen?blended natural gas high?pressure pipelines in open space by integrating the pipeline leakage model,nominal nozzle model and jet in cross?flow integration model,verified the applicability of the jet in cross?flow integration model under high?speed jet and analyzed the influence of hydrogen ratio,wind speed leakage hole diameter and pipeline pressure on the leakage jet trajectory and the influence of hydrogen ratio,wind speed and nominal diameter on the maximum explosion danger distance.The results shows that the JICF model is in good agreement with the experimental data and the numerical simulation data.The greater the hydrogen mixing ratio,the diameter of the leakage hole and the pipeline pressure are,the less the deflection degree of the leakage jet trajectory will be.The higher the wind speed is,the greater the deflection degree of the leakage jet will be.The relationship between the hydrogen ratio and the maximum dangerous explosion distance decreases linearly when the hydrogen ratio is lower than 44.4%,and increases linearly when the hydrogen ratio is higher than 44.4%.The relationship between the wind speed and the maximum dangerous explosion distance is approximately linear.The nominal diameter is directly proportional to the maximum explosive danger distance.