A 4—UPS—UPU spatial 5-DOF parallel robot mechanism was introduced. A dynamics model of 4—UPS—UPU was presented. The kinematics of the UPS and UPU chain of leg was analyzed and the velocity mapping relationships between the parts and the driving axis were established. The exterior force load and the equivalent driving force were educed. The dynamics model of 4—UPS—UPU parallel robot mechanism was educed by the virtual work principle approach, which was the foundation of the dynamic analysis. Combined with engineering application examples, numerical verification and virtual simulation verification of the results of driving force and constraining torque was carried out.