• A universal vehicle-wheel-ground coupling modeling method of all-terrain DDUGV with variable structure is proposed. • Based on Bekker-Wong-Janosi theoretical model and co-calibration of geotechnics experiment and DEM simulation, the mathematical model of wheel- soil interaction is verified and optimized, which is much more efficiency than Discrete Element Method (DEM) simulation. • The coupling model can simulate the real vehicle system by considering strong nonlinear factors and time delaying of hydraulic system and electric driving system. • Newton-PSO algorithm is established to simplify the problem of solving theoretical mathematical model of wheel-soil interaction and prevent chattering and sawtooth phenomenon during simulation. • The accuracy and computation efficiency of the coupling model are verified by co-simulation results. The establishment of a dynamic model of distributed driving unmanned ground vehicle (DDUGV) is the premise of vehicle state identification and high-quality control. However, due to the strong nonlinearity of the DDUGV system itself, the various external influence and the difficulties of real-time calculating, the simulation results based on existing conditions are far from the actual vehicle test results, resulting in the huge gap between the simulation test and the actual engineering practice. Regarding the problem mentioned above, this paper takes the 3-axles DDUGV with variable structure as the research object, and proposes a universal dynamic modeling method for DDUGV, which considers the uncertainty of terrain and variable structural parameters. Firstly, based on Newtonian mechanics, mathematical models of the vehicle's variable structure, body posture, static/dynamic suspension, hydraulic transmission, wheel and in-wheel motors are established. Secondly, taking the wheel as the coupling node between vehicle dynamics and ground mechanics, 3 tire models in typical driving environments are established, which are the magic tire model used in paved road, and the Bekker-Wong-Janosi theoretical model used in sandy and clay soil, respectively. Thirdly, based on the established mathematical model, a universal DDUGV modeling method is proposed. Then, based on the co-calibration of geotechnics and discrete element method (DEM), the particle parameters of sandy soil are obtained and the theoretical mathematical model of wheel-soil interaction is verified and optimized. Finally, based on the established vehicle-wheel-ground coupling model of the 3-axles DDUGV with variable structures, simulation tests are carried out under typical working conditions, which are compared with the results of existing vehicle dynamics software to verify the accuracy, computation efficiency and real-time property. The vehicle-wheel-ground coupling dynamic model established in this paper can provide a reference for the construction of the vehicle dynamic models, the analysis of driving characteristics, and the research of control strategies in complex environment. [ABSTRACT FROM AUTHOR]