Abstract: Using the automotive theory and terra-mechanics theory,steering dynamic models of the rover in two different coordinates(relative coordinate and fixed coordinate) are established,respectively.Two characteristic equations of the models under two different coordinates are deduced and compared.Resultsshow that the two models are consistent in nature and are both analytical linear different equations with multiple inputs and multiple outputs.Based on the analysis of the equations and their eigenvalue equations,the specific relationships among the rover's running performances,the main structure parameters of the rover and the travel speed are obtained.All these relationships provide a theoretical basis for further research on the steering dynamic characteristics and motion control of rovers.Finally,the simulation validates that the rover should be chosen according to the vehicle mass,structural parameter,surface conditions,and other factors,but not the smaller the better.