Topsoil mantle is very important in grassland protection against sandy desertification in the form of blowouts. Regardless many researches, little attention has been paid on the destructive impacts of vehicle traffic on the topsoil mantle. In this research, field investigation, load test, light cone dynamic penetration, and laboratory tests was applied to assess the impacts of vehicle traffic on the topsoil physic-mechanical and shear deformation properties, at different erosion extent regarding the topsoil mantle ranging at the depths from zero to thirty centimeter. It was discovered that in contrast with the original grassland, topsoil compressibility decrease, shearing strength and bearing capacity increase, along with the increase of the depth of tracks in use by off road vehicles. The topsoil surface hardens quicker than the lower level, accelerating grassland vegetation degradation. Insufficient of the bearing capacity result in overall shear failure and entailed vibration creep or liquefaction makes the soil mantle out of stability and to dismantle. Vehicle compact on the original grassland topsoil mantle resulted in vibration compaction settlement and irreversible shear deformation, destructed topsoil mantle original structure due to its higher compressibility and stress concentration phenomena. Therefore off road vehicle traffic facilitates wind and/or runoff to create holes in the topsoil to generate blowouts, and then large scale sandy desertification occurs.