Abstract: To address the issue that the thermal load control is understudied when the fuel thermal efficiency of diesel engines is achieved, a collaborative optimization research on the piston bowl shape and fuel injector, and an analysis of the thermal load distribution of different combustion system were conducted based on AVL FIRE software. The simulation results show that the combustion chamber scheme Bowl_A with a larger throat depth should be matched with a smaller fuel injector spray angle (144°), while Bowl_B, featuring a smaller throat depth, requires a larger spray angle (149°). The high-pressure indicated specific fuel consumption (HPISFC) of both configurations was comparable at the operating point corresponding to the optimal brake thermal efficiency, exhibiting an approximately 3.9% reduction relative to the original combustion chamber. For the Bowl_B scheme, flow-guiding lines were designed at the opening of the piston bowl to split the heat flux on the firedeck. Its average heat flux only increased by 5.2% compared with that of the original bowl, and the peak solid temperature of the firedeck reached 365 ℃, which met the reliability requirements. Experimental verification of the Bowl_B scheme show that the calculated trend of brake specific fuel consumption and soot emission variation with the fuel injector spray angle aligns with the experimental results.