Abstract The ring-rolling design for a large-scale ring product of Ti–6Al–4V alloy was investigated by a calculation method and FEM analysis. The ring-rolling design includes geometry design (rolled ring dimensions, blank and billet size, etc.) and optimization of process variables. The design criteria are to achieve minimal forming loads, uniform distributions of strain and temperature, and defect-free ring products. In order to predict the forming defects such as the flow localization or instability, shear bands and surface cracks, the processing-map approach considering flow instability was used with FEM simulation. The experimental analysis based on the flow instability map approach was carried out to predict the formation of rolling defects in plane-rolled Ti–6Al–4V rings. An optimum process design to obtain sound Ti–6Al–4V rings without forming defects was suggested and its validation was made by the comparison between the experimental data and FE analysis results.