Abstract: To evaluate the stability of reversed austenite under the condition of stress and low temperature, the morphologies of reversed austenite in 9Ni steel after the treatments of quenching + tempering (QT) and quenching + lamellar quenching + tempering (QLT) were observed by transmission electron microscopy. Reversed austenite in the QT-treated sample is most lath-like; but in the QLT-treated sample, both thin foil and lath reversed austenite can be discovered and the former mainly turns up along lath martensite. The amount of reversed austenite and its carbon content before and after soaking in liquefied nitrogen were measured by X-ray diffraction. More stable reversed austenite is detected in the QLT-treated sample after soaking in liquefied nitrogen. The mechanical stability of reversed austenite was gauged by bending, uniaxial tensile and compression tests. Both the tensile and compress stress promote the reversed austenite to transform, and most of residual austenite are revealed within grains.