Vehicles with varying loads deform soft-soil grounds， and the depth of their wheel intrusion is a crucial parameter for evaluating vehicle trafficability on soft soil. This study introduces a novel method that combines the Continuum-Discontinuum Element Method （CDEM） and Material Point Method （MPM） to create a coupling model of wheel and soft-soil interaction and simulate their interaction process. The model analyzes the relationship between different variables， including the wheel load； elastic modulus， strength parameters （cohesion and friction angle）， and surface stress of the soft soil； and intrusion depth， to quantify the law of wheel intrusion depth on soft soil. The results indicate that the intrusion depth positively correlates with the wheel load， with a relative variation of approximately 179%， and negatively correlates with the elastic modulus and strength parameters in a non-linear manner， with relative variations of approximately 23% and 164%， respectively. When the wheel load is constant， the intrusion depth is more sensitive to the strength parameters of the soft soil. The three-dimensional relationship established between the strength parameters and intrusion depth provides a theoretical foundation for key parameter measurements in evaluating vehicle trafficability on soft soil.