The multi-roller straightening process of section steel is analyzed by the springback theory of small curvature plane bending.The theoretical analysis results prove the curvature unification in straightening process and clearly reveal the principle of the multi-roller straightening process.The principle can be described as:the initial curvatures are reduced by several times anti-bending;meanwhile the initial curvature differences are diminished and the residual curvatures are unified;finally,the member after curvature unification is straightened by the last anti-bending.With the plastic region ratios becoming larger,the initial curvatures are more easily unified in straightening process.Based on the plastic region ratios and the required number of roller systems for unifying the initial curvatures,the large deformation straightening strategy and the small deformation straightening strategy are redefined.The new definition provides an important theoretical basis for setting reliable reduction rules.Through the theoretical analysis results,a new straightener design philosophy is proposed to improve the straightening quality and further increase the adjustment precision as well as the flexibility of the last roller system.The adjustable end roller emerges as the times required,achieving agood effect in practical application. The multi-roller straightening process of section steel is analyzed by the springback theory of small curvature plane bending. The theoretical analysis results prove the curvature unification in straightening process and clearly reveal the principle of the multi-roller straightening process. The principle can be described as: the initial curvatures are reduced by several times anti-bending; meanwhile the initial curvature differences are diminished and the residual curvatures are unified; finally, the member after curvature unification is straightened by the last anti-bending. larger, the initial curvatures are more easily unified in straightening process.Based on the plastic region ratios and the required number of roller systems for unifying the initial curvatures, the large deformation straightening strategy and the small deformation straightening strategy are redefined.The new definition provides an important theoretical basis for setting reliable red uction rules.Through the theoretical analysis results, a new straightener design philosophy is proposed to improve the straightening quality and further increase the adjustment precision as well as the flexibility of the last roller system. Adjustable end roller emerges as the times required, achieving agood effect in practical application.