Discrete Variational Method （DVM） was adopted in the first principles calculation of hydrogen occupation between γ and γ＇ in precipitate strengthened austenite alloys to analysis the mechanism of hydrogen embrittlement of them. It is indicated that hydrogen inclined to enter the octahedral interstitial site in the γ matrix instead of interstitial site of γ＇ phase or γ-γ＇ boundary when the misfit of γ/γ＇ is in the common range of the γ＇ strengthened austenite alloys and small variation of the misfit will not change the situation. Contrariwise, hydrogen is inclined to enter γ＇ phase when there is strain to some extent, corresponding to the misfit is higher than that of 3.7% or the size of γ＇ phase is big enough. Hydrogen in the γ＇ phase causes the localization and asymmetry of the bend between metal atoms, which may induce the slip localization of γ＇ phase and thus cause hydrogen embrittlement of alloys.
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