Abstract: High purity hot hydrogn charging at high temperature was used to investigate the hydrogen embrittlement (HE) of JBK-75 alloys with different contents of P and Si(Mn). The results indicated that by lowering P content, the size and distribution γ' precipitate became more homogeneous and the precipitation of stable phase η was retarded, thus the hydrogen resistant properties of the alloy wes obviously improved; however, when Si(Mn) content was lowered together with P, though the size and density of γ' were also homogeneous and no η phase was observed, formation of some micro twin around grain boundaries was found to be detrimental to the hydrogen performance of the alloy. and hydrogen induced loss of area reduction was very high. Therefore, to improve the hydrogen resistant properties of the alloy, P content should be lowered while certain amount of Si(Mn) should be kept