Abstract: Regolith is a vital terrain feature in small body surface exploration missions. For simulating the low-velocity collision between the probe and the regolith during landing, the terramechanics theory is applied to describe the regolith topography in the weak irregular gravitational field of the asteroids. The newly-proposed simulation method in this paper can simultaneously solve the 6-DOF motion of the probe and the collision process of the regolith surfaces. By exploiting this method, the collision evolution between the different-sized cube probes and the asteroid regolith is analyzed. The influence of the edge length of the cube on the low-velocity collision duration time, the velocity, the angular velocity, and the regolith deformation is investigated.