The　lack　of　hydrogen　(H2)　transportation　infrastructure　restricts　the　development　of　the　H2　industry.　Owing　to　the　high　investment　of　building　specific　facilities,　using　existing　natural　gas　(NG)　pipelines　to　transport　a　blend　of　H2　and　NG　(H2NG)　is　a　viable　means　of　transportation　and　approach　for　large-scale　long-time　storage.　However,　variation　in　the　thermo-physical　properties　of　an　H2NG　blend　will　impact　the　performance　of　pipeline　appliances.　To　address　the　gaps　in　H2　transmission　via　an　NG　system　in　the　context　of　energy　consumption,　in　the　present　paper,　a　one-dimensional　pipeline　model　is　proposed　to　predict　the　blended　flow　in　a　real　existing　pipeline　(Shan–Jing　I,　China).　The　data　of　NG　components　were　derived　from　real　gas　fields.　Furthermore,　the　influence　of　H2　fractions　on　pipeline　energy　coefficient　and　the　layout　of　pressurization　stations　are　comprehensively　analyzed.　In　addition,　the　case　of　intermediate　gas　injection　is　investigated,　and　the　effects　of　injection　positions　are　studied.　This　study　serves　as　a　useful　reference　for　the　design　of　an　H2NG　pipeline　system.　The　present　study　reveals　that　with　the　increasing　in　H2　fraction,　the　distance　between　pressure　stations　increases.　Furthermore,　when　the　arrangement　of　original　pressure　stations　is　maintained,　overpressure　occur.　Intermediate　gas　injection　results　in　the　inlet　pressure　of　subsequent　pressurization　stations　reducing.　Using　existing　pipeline　network　to　transport　H2NG,　it　is　necessary　to　make　appropriate　adjustment.　©　Copyright　©　2021　Liu,　Teng,　Liu,　Han　and　Li.