Abstract: With the depletion of terrestrial mineral resources, the deep-sea mineral resources have become the focus of exploitation and utilization in all countries of the world. A deep-sea mining car is an important equipment for deep-sea mineral resources mining, and a soft marine sediment is a special substrate with very low bearing capacity and shear strength. In mining operations, the physical and mechanical properties of soft marine sediment directly affect the stability of mining vehicles. The Burger's contact model was selected as the constitutive model of deep-sea soft sediment, and a laboratory triaxial test was carried out on seafloor soft undisturbed soil in a certain area. By comparing the actual triaxial test with PFC3D particle flow numerical simulation experiment, parameters of the Burger's creep model of soft sediment were calibrated. Meanwhile, the corresponding parameters were modified according to the calibration results, the digital simulation model of the seabed mining vehicle was established under five working conditions with different soil beds, and the subsidence depth of the mining car under different driving speeds under each working condition was simulated. The results show that the subsidence depth changes nonlinearly with the driving speed, and the subsidence depth decreases with the increasing of the speed in a certain range and gradually tends to be stable. In addition, the soft sediment in the creep area features higher clay content (38.1%～48.4%), water content (88.13%～137.79%), and compressibility (compression coefficient: 1.86～3.73 MPa⁻¹, compression modulus: 1.26～2.13 MPa), and lower density (1.3～1.5 g/cm³) and strength (penetration resistance: 0.19～1.32 N, cohesion: 3.7～6.9 kPa, internal friction angle: 2.4°～3.9°), indicating that the bearing capacity is low and the creep performance is strong. This study provided a reference on a macro level and a theoretical basis for safe operation of seabed mining vehicle on soft bottom with similar parameters.