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To enhance the strength of metastable austenitic stainless steel (ASS) sheet components, a novel method was proposed for the strengthening of a metastable ASS dome by a newly designed bulging device under deep cryogenic conditions. The load curves, Vickers microhardness, thickness distribution, and deformation law of formed dome components at room temperature (RT) and cryogenic temperature (CT) were discussed in detail. The strengthening mechanism of metastable ASS domes was elucidated by phase transformation, and the evolutions of grain boundary and dislocation at RT and CT, respectively. It is found that the strength of metastable ASS domes at CT increases with increasing strain. The strengthening effect of the metastable ASS sheet under biaxial stress state is significantly enhanced. Less martensite is generated at a low plastic strain, and the stability of the austenite phase is noticeably decreased under a large strain at CT. The dislocation distribution at RT is relatively uniform and is not accumulated at grain boundaries, while numerous dislocations at CT are apparently distributed near grain boundaries. The forming of metastable ASS domes at deep cryogenic temperatures is accommodated by both dislocation slip and martensitic transformation. Hence, the strength of metastable ASS thin-walled domes is significantly improved. (1) A novel method was proposed for the strengthening of metastable austenitic stainless steel (ASS) sheet by a newly-designed bulging device under deep cryogenic conditions. (2) Based on the quasi-in situ EBSD observations, the strengthening mechanism of metastable ASS domes was elucidated by microstructural phase transformation, and the evolutions of grain boundary and dislocation at room temperature (RT) and cryogenic temperature (CT). (3) Under the condition of low temperature biaxial stress, the strengthening effect of the metastable ASS sheet is significantly enhanced. Compared to RT, the maximum force increases from 105 to 182 kN at CT. The Vickers hardness increases to 393 HV at CT for the 20 mm dome, which is 38.9% higher than that at RT. (4) The stability of the austenite phase at a large plastic strain is noticeably decreased at CT. Martensitic transformation induced by a great strain is drastic. (5) The forming of metastable ASS domes at low cryogenic temperatures is microstructurally accommodated by dislocation slip and martensitic transformation. [ABSTRACT FROM AUTHOR]