Abstract: Agricultural diesel engines are widely equipped with inclusive combustion at present. However, the relatively low level of the in-cylinder combustion can directly cause the higher specific fuel consumption and soot emissions. Particularly, such engines are operated under plateau conditions, where the oxygen concentration in the air is significantly lower compared with the plain areas. In this research, the vertical injection angle (VIA) matching strategy was proposed for the TCD combustion of the agricultural diesel engines in the plateau regions. The abbreviation of the TCD was as follows, where the letter “T” was a turbocharger, “C” referred to charge air cooling, and “D” was a diesel particle filter. A wall-guiding model of the TCD combustion was established using the AVL Fire software. A systematic investigation was also made on the influence of the VIA patterns on the combustion and emission performance of the TCD combustion under various load conditions in plateau environments. Meanwhile, the VIA matching mechanism on the in-cylinder fuel-air mixture was clarified for the engine under different engine loads in plateau areas. The results showed that: 1) Under the high (100% and 75%) of the full engine load, the greater VIA gradually reduced the performance of the TCD combustion in the plateau areas. In contrast, the combustion performance deteriorated rapidly when the VIA was excessively small. Among them, a relatively rich fuel-air mixture tended to accumulate in both the bottom arc and the central region of the combustion chamber at the end of the fuel injection. 2) Under the medium (50%) and low (25%) levels of the full engine load, the smaller VIA caused a gradual decline in the combustion performance. While an excessively large VIA rapidly deteriorated the combustion performance. In this case, the relatively rich fuel-air mixture was primarily gathered near the cylinder head region of the combustion chamber, after the fuel injection was fully completed. 3) The optimal VIA values were determined to be 143°, 144°, 146°, and 146°, respectively, when the TCD combustion was operated under the engine loads of 100%, 75%, 50%, and 25%. Furthermore, the optimal VIA matching gradually decreased with the increase in the engine load, and the sensitivity of the combustion performance to the VIA increased. 4) The optimal performance of the diesel engine was achieved in the VIA matching at the high (75%) load for the TCD combustion in the plateau areas. 5) Experiments also verified that the performance of the TCD combustion was significantly improved, compared with the original. An appropriate VIA matching was attributed to the fuel-air mixing, due to the guiding behavior of the annular raised structure on the wall surface of the combustion chamber in the TCD combustion. Once the engine load was ranged from 25% to 100%, the TCD combustion was achieved in the effective fuel consumption rate by 7.2 to 12.8 g/(kW·h), while the soot emissions were reduced by 60% to 91%, compared with the original. The finding can also provide a theoretical and technical reference to optimize the performance of the diesel engines under plateau environmental conditions.