Abstract: The uneven deformation during the H-beams rolling primarily occurs during the opening of the special-shaped billets, and the control of dimensional precision in the rolling of special-shaped sections significantly impacts subsequent universal rolling processes. To this end, the finite element analysis software MARC/SuperForm was utilized to simulate the opening rolling process of a special-shaped billet with dimensions of 900 mm × 510 mm × 130 mm, and to analyze the key factors and influencing mechanisms of web thickness changes. Based on the simulation results, the existing H-beam billet cutting procedure was optimized by adjusting the distribution of pressing amount, reducing the pressing amount of the last pass of the web plate.This adjustment aimed to minimize the difference in elongation rates between the web and the flange, thereby reducing the extent of web thickening.The results indicate that the web thickness significantly increases near the exit of the deformation zone, and the thickness of the web plate increased by 8.4 mm compared to the set thickness at the end of billet opening, mainly due to the difference in elongation between the web plate and the flange.In the deformation zone, the metal in the web experiences triaxial pressure. As the rolled piece exits the deformation zone, the pressure from the rolls and lateral resistance gradually dissipates, but the rolling pressure exerted by the flange on the web does not immediately diminish, causing the web to continue experiencing axial compressive stress, which leads to further thickening. Typically, the elongation rate of the web is greater than that of the flange, and this difference becomes more pronounced, especially under higher reductions, resulting in a greater increase in thickness after exiting the deformation zone. For the optimized H-beam billet cutting procedure, after the billet rolling is completed, the thickness increase of the web plate is reduced from the original 8.4 mm to 3.7 mm, effectively improving the accuracy of the web plate size.