Based on the actual road operation data obtained from China Ⅵ remote emission monitoring platform of 385 heavy-duty vehicles, the low-load operating characteristics and NO_x emission features of China heavy-duty vehicles were analyzed by employing techniques such as the micro-trip window method and peak-by-peak fitting according to the U.S. Low Load Cycle (LLC) methodology. The results reveal that the median window load for heavy-duty vehicles in China is below 20%, and the load that remains below 20% during transient operating conditions accounts for more than 57%. Within the load range, the lower exhaust temperature leads to reduced catalytic efficiency of aftertreatment system and obvious increase of NO_x emissions. Furthermore, the window load distribution demonstrates a "single-peak" pattern concentrated between 0% and 40%, which differs significantly from the load distribution of heavyduty vehicles in the United States. Accordingly, an average load of 13% or less is proposed to be set as the upper limit for the low-load operating conditions window for heavy-duty vehicles in China, which provides a reference for establishing low-load operating conditions that are suited to the actual on-road operating characteristics of domestic heavy-duty vehicles. In addition, the current NO_x sensor dew point protection strategy leads to the exclusion of 14.60% to 23.88% of high-emission operating duration from supervision, necessitating urgent attention.