By taking the two-stage planetary roller screw mechanism （PRSM） as the research object，this paper supplements the strength conditions and the stability requirements of the compressed rod required for its parameter design.And，on the basis of motion principle of the two-stage PRSM，the theoretical calculation methods of the rotation and revolution angular velocity of the rollers，the axial displacement and axial velocity of the nut at each stage are proposed.Then，according to the design parameters，a three-dimension model of the two-stage planetary roller screw mechanism is established，and a multi-body dynamics simulation model is constructed based on ADAMS software.By comparing the theoretical values with the simulation results，it is found that the relative errors are within the acceptable range，which verifies the rationality of the parameter matching of the two-stage PRSM and the accuracy of the theoretical calculation method.