In order to improve the drying performance of the 5H-2 grain dryer, an innovative modification was introduced by transforming the conventional angular boxes into porous angular boxes. Computational fluid dynamics (CFD) simulations using Fluent were employed to analyze the airflow field within the drying segment of these newly designed porous structures. A comparison of the temperature distribution within the drying chamber under unloaded conditions revealed a notably more uniform temperature field with the implementation of the porous angular boxes compared to their non-porous predecessors. Experimental drying trials were subsequently conducted on early-season rice variety ‘Zhongzao 35’ using the 5H-2 grain dryer equipped with these porous angular boxes. The tests were configured with a hot air drying temperature of 65 °C, an air velocity of 8 m/s, and a drying-relaxation ratio of 1∶2. The resultant drying rates ranged from 0.798%/h to 1.002%/h, with an increase in kernel cracking rate of 7.4% to 10.2% post-drying. In comparison to the original angular box design, the dryer equipped with porous boxes demonstrated a significant enhancement in drying efficiency, with rates elevated by 12.1% to 21.2%, while concurrently reducing the increase in kernel cracking rate by 1.9% to 5.1%. These findings underscore the efficacy of the porous angular box design in optimizing the drying process, thereby reducing grain damage and enhancing overall drying performance.