Abstract: Black carbon (BC) emissions from diesel vehicles have serious impacts on air quality and climate change. However, there are still many limitations in the development of diesel vehicle BC emission inventory in China. In order to improve the accuracy of black carbon emission inventory of diesel vehicles, the effects of different emission standards, driving cycles and load conditions on BC emissions from heavy-duty diesel trucks (HDDT) were analyzed by using heavy duty truck chassis dynamometer sampling and thermo-optic reflection black carbon measurement. The results show that upgrading the emission standards had an significant impact on the BC emissions of HDDT. Compared with the trucks with China Ⅰ and Ⅱ, the proportion of BC in particulate matter (PM) of the tested trucks with China Ⅲ, China Ⅳ and China Ⅴ gradually increased from 41% to 72%. The driving cycles also had influence on the BC emissions. The BC ratios on C-WTVC driving cycle (the driving cycle adapted to the fuel consumption test for heavy-duty commercial vehicles in China) were 5%-10% higher than those on VECC driving cycle (the typical roads driving cycle for heavy-duty commercial vehicles in China). The BC ratios of HDDT with full loads were higher than the half-loaded ones. For China Ⅱ heavy trucks, the differences were about 15%. The BC ratios of China Ⅲ and Ⅳ heavy trucks at full load were about 7%-8% higher than those at half loads. Emission standards, driving cycles and load conditions should be considered comprehensively when determining the BC emission factors. Applying a fixed ratio in PM to calculate BC emission factors can introduce large uncertainties in the BC emission inventory.