China has a large mileage base of low-grade highways, and accidents caused by brake failure of heavy-duty trucks occur frequently. To conduct an in-depth study on the braking behavior of truck drivers on continuous downhill sections of low-grade highways, this research, based on the field-measured data of six-axle articulated trains on low-grade highways during long downhill driving, identified the driver’s braking timing on downhill sections with complex horizontal and vertical alignments, analyzed and quantified the characteristics of truck drivers’ braking behavior on continuous downhill sections of low-grade highways. Furthermore, a joint simulation model of driver behavior (integrating Matlab/Simulink) was established in the TruckSim simulation software, and the reliability of the model was verified through comparison.The results show that:On horizontal curve sections, affected by the curve, drivers exhibit relatively high-intensity braking behavior at the end of straight sections and the start of curve sections;On straight downhill sections with a gradient of 2%~9%, the drivers’ braking magnitude is positively correlated with the gradient;When curves are classified into sharp curves, medium curves, and gentle curves based on radius, the average braking magnitude before entering sharp curves reaches 220 mm, while there is no significant difference in the average brake pedal stroke between medium curves and gentle curves, with their average braking magnitudes reaching 176 mm and 174 mm, respectively.Compared with the brake drum temperature rise prediction models in previous studies that did not consider horizontal alignment factors, the simulation model established in this research has higher prediction accuracy for brake drum temperature. It can provide a theoretical basis for strengthening traffic safety guarantees on low-grade highways.