Abstract: The effects of deformation on the reversed austenite and mechanical properties of ultra-low carbon bainitic steel were studied by means of hardness test, tensile test, metallographic examination, X-ray diffraction test, transmission electron microscopy and energy spectrum analysis. The results show that the hardness and strength of ultra-low carbon bainitic steel increased significantly with the increase of cold rolling reduction. The volume fraction of austenite in ultra-low carbon bainitic steel gradually increased from 0.4% to 14.85% when the deformation was 90%. The reversed austenite in the steel was mainly distributed at the grain boundary, and its morphology changed from film-like to block-like. The mass fraction of Ni and Mn in austenite decreased with the increase of deformation. The mass fraction of Ni decreased from 59% to 11.64% when the deformation was 90%, and the mass fraction of Mn decreased from 16% to 3.48% when the deformation was 90%.