Taking dismantling machine as the research object, the kinematical mathematic model was established by using the D-H method. The positive kinematics equation of the model was obtained. Combining with Monte Carlo method, the nephogram of workspace was obtained, and the limit position and the relationship with each part of the working device were defined. Then the threedimensional model was established for simulation in ADAMS. The simulation of the structure was carried out, and the trajectory curve of hydraulic shear was gotten. In comparison of the working space diagram, the two results were basically consistent. The analysis result shows that the D-H coordinates and the Monte Carlo method can improve the design efficiency and provide reference for the actual application of dismantling machine.