Specialized heavy-duty multi-axle electric drive vehicles are commonly used in aerospace engineering to transport weapons and strategic materials, whose mechanical structure and dynamic performance emerging are always a hot spot in the field of aerospace and mechanical fields. At the same time, SIMPACK, a robust multi-body dynamics simulation software, is seldom utilized in the modeling of passenger vehicles and lacks established methodologies for modeling specialized heavy-duty multi-axle electric drive vehicles. Addressing this gap, this study investigates modeling approaches for a 8 × 8 heavy-duty vehicle, focusing on its unique structure and operational principles. Using the modular methodology, the vehicle was divided into distinct components—cab, frame, suspension, wheels, steering, and powertrain—to construct a comprehensive vehicle model in SIMPACK. Simulations under various operating conditions were performed, and the simulated data were validated against empirical test data to ensure model accuracy. Results indicate that the dynamic indicators of the simulated vehicle fall within an acceptable range. This study provides a reference framework for future dynamic research on specialized heavy-duty multi-axle electric drive vehicles.