This paper describes the mathematical modeling and the propulsive characteristics of a novel robot driven by Archimedean screw mechanisms, named Screw Drive Rover. For secure locomotion on soft soil, the proposed rover would become one of the good solutions because of its robustness to slipping and getting stuck in the soil. Furthermore, the rover is expected to move in various directions by using the dual screw units. However, the interaction between such screw unit and the surrounding soil is quite complicated and remains undefined. So, this paper attempts to model the tractive effort of the rover on the soil. The mathematical modeling is newly developed based upon terramechanics, addressing soil-vehicle interactive mechanics. Finally, the validity of the proposed model is demonstrated by simulation analyses.