Abstract：The dynamics model of 3-UPS parallel mechanism with three degrees of freedom is created in order to determine the moving relations of the wriggle turning joints for a move-in-mud robot. After reviewed some relative researches on move-in-mud robot, a parallel mechanism with three degrees of freedom is given which can accomplish straight and turning movement. Based on the analysis on the moving characteristics of 3-UPS parallel mechanism, the kinematics model of this mechanism is created firstly, so as to obtain the relational expression of velocity and acceleration of moving platform and each branch chain. Then, based on the Lagrange equation, the dynamics model of 3-UPS parallel mechanism is established to solve the total driving force and torque of the whole system and the drive force of each active lever. By using software of Matlab, the simulation analysis on the dynamics model as mentioned above is carried out to get some changing curves about drive force and torque. These works provide the foundation for the design of control system of move-in-mud robot and give a reference to the dynamics analysis of parallel mechanism with few degrees of freedom.