Abstract: At present, most agricultural diesel engines are equipped with traditional inclusive combustion systems, which are primarily based on the ω combustion system. The combustion level within the cylinder of these engines is relatively low, leading to higher specific fuel consumption and increased soot emissions. This issue is especially pronounced in the oxygen-deficient environments typically found at high altitudes. In order to optimize the performance of agricultural diesel engines in plateau environments, this study focuses on high-altitude agricultural diesel engines as the research subject. The study uses AVL Fire software to create a wall-directing type TCD combustion system model. The TCD stands for Turbocharger (T), Charge air cooling (C), and Diesel particulate filter (D). The aim is to investigate how the vertical injection angle (VIA) affects the combustion and emission performance of the system under different load conditions. The research also explores the influence mechanism of VIA on the fuel-air mixing characteristics within the combustion chamber under high-altitude conditions. Furthermore, the study seeks to clarify the matching rules of VIA under various load conditions and propose a VIA matching strategy for the TCD combustion system of plateau agricultural diesel engines. The results of the study reveal several important findings. 1) under the conditions of high load (100% and 75% loads) in the plateau environment, when the VIA is relatively large, the combustion performance of the TCD combustion system decreases slowly. However, when the VIA is too small, the combustion performance drops sharply. After the completion of fuel injection, a relatively rich mixture accumulates in the bottom arc and central area of the combustion chamber, which negatively affects combustion efficiency. 2) Under medium and low load conditions (50% and 25% loads), the effects of VIA are different. When the VIA is too small, the combustion performance decreases slowly, but when the VIA is too large, the performance drops sharply. In this case, a relatively rich mixture accumulates near the combustion chamber and cylinder head after fuel injection. This again indicates that an improper VIA disrupts the balance of fuel and air mixing in the combustion chamber, which hinders combustion efficiency. 3) The study identifies the optimal VIA for the TCD combustion system at different load conditions. Specifically, the optimal oil beam angles for the system at 100%, 75%, 50%, and 25% load conditions are 143°, 144°, 146°, and 146°, respectively. This data suggests that as the load increases, the optimal VIA gradually decreases. Moreover, the system’s combustion performance becomes more sensitive to changes in VIA as the load increases. 4) Based on these findings, the study proposes a VIA matching strategy for the TCD combustion system of high-altitude agricultural diesel engines. The strategy recommends adopting a high-load (75% load) working condition for VIA matching, as this results in the best overall performance across different load conditions. 5) Experimental verification of the VIA matching strategy demonstrates its effectiveness. After the TCD system was matched with the optimal VIA, the fuel spray interacts with a ring-shaped protruding structure on the wall, creating a swirling flow that enhances the mixing of fuel and air. This improvement in fuel-air mixing significantly boosts the combustion performance compared to the original ω combustion system. The effective fuel consumption rate is reduced by 7.2 to 12.8 g/(kW·h) under load conditions ranging from 25% to 100%, indicating a substantial reduction in fuel consumption. Additionally, the smoke density is decreased by 60% to 91%. The results of this study provide a theoretical basis and technical reference for the future design improvements and performance enhancements of diesel engines operating in challenging plateau environments.