This study investigated the dominant factors and patterns of change in heat flow variations of diesel engine with respect to altitude and intercooler temperature，with the aim of addressing the issue of efficient thermal management of diesel engine in high-altitude environments. The results indicate that the dominant factors for the heat removed by the intercooler and coolant are temperature differences，while the heat removed by exhaust is mainly affected by intake/exhaust temperature difference during intercooler temperature changes，and by exhaust mass flow during altitude changes. At a constant altitude，for every 10℃ increase in intercooler temperature，the effective power of the diesel engine，the heat removed by intercooler，and the proportion of miscellaneous heat losses decrease by an average of 0.08%，0.79%，and 0.23%，respectively. Conversely，the proportion of heat removed by exhaust and coolant increases by an average of 0.48% and 0.62%，respectively，indicating more fuel heat is transferred to exhaust and coolant，increasing the cooling load. At a constant intercooler temperature，for every 1000m increase in altitude，the effective power of the diesel engine and the proportion of heat removed by exhaust decrease by an average of 0.44% and 1.37%，respectively. Meanwhile，the proportion of heat removed by intercooler，coolant，and miscellaneous heat losses increases by an average of 0.93%，0.25%，and 0.62%，respectively. This indicates a greater heat transfer toward the intercooler and coolant，suggesting that the intercooler and cooling systems should provide sufficient thermal margin for diesel engine operation at high altitudes.