<p>To completely cure the internal shrinkage cavity defects of continuous casting billets, the hot core heavy reduction rolling process (HHR²) is proposed. Through pilot-scale tests and numerical simulations, its mechanism of action and optimization approaches were deeply analyzed. The traditional process still cannot completely close the 4&#xa0;mm void when the single-pass reduction rate is ≥ 22.2%. The HHR² process only requires a compression rate of 21.5% to achieve complete void closure. The void height is significantly reduced by 60%-73%, and the average compression rate reaches 66.1%. The research reveals that the synergistic effect between the roller diameter and the reduction amount is the core mechanism: increasing the roller diameter (250 to 1050&#xa0;mm) extends the contact arc length by approximately 30%, forming an effective three-directional compressive stress field, significantly enhancing the reduction efficiency by 25%, but accompanied by an increase of 15–20% in the consumption of plastic work; the increase in the reduction amount (increment from 6 to 36&#xa0;mm) enhances the plastic deformation energy and reduces the residual rate of pore volume from 0.358 to &lt; 0.1. By constructing a nonlinear prediction model and introducing the plastic work index coefficient and the high-order term of the shape factor, the prediction accuracy of the model is significantly improved (<i>R</i> = 0.99), which is superior to the linear model (<i>R</i> = 0.98), and can effectively guide the optimization of dynamic process parameters. For example, under the conditions of a roller diameter of 750&#xa0;mm and a reduction of 30&#xa0;mm, the reduction efficiency is increased by 15% and the energy consumption is reduced by 8–10%. Furthermore, the HHR² process significantly improved the mechanical properties of the material (12–18%). This research provides theoretical support for the production of high-quality continuous casting billets.</p>