This study employs numerical simulation to investigate the impact of a dual-passage prechamber system on the performance and emissions of a heavy-duty diesel engine under highload conditions. By optimizing the passage angle and diameter of the dual-passage prechamber, the indicated thermal efficiency is improved and soot emissions are reduced, while NOx emissions remain largely unchanged.The results indicate that, under high-load conditions, the dual-passage prechamber system shortens the combustion duration, ensures a favorable combustion phase, enhances turbulence kinetic energy during the late combustion stage, and strengthens soot oxidation, thereby improving the indicated thermal efficiency. The optimal configuration is determined to be a channel angle of 30° between the two passage, an inclination angle of 30° between the passage and the main combustion chamber, and a passage diameter of 2mm. This configuration increases the indicated thermal efficiency by 0.12% and reduces soot emissions by 31.84%, with NOx emissions remaining largely unchanged compared to the original engine.