Abstract: In order to solve the partial fracture of the spade arm for 4YS-600 type tree transplanter, the spatial location and the improvement scheme were optimized based on the force, motion and space geometry. Three-dimensional modeling and motion simulation of the tree transplanter were finished by Pro/E and ADAMS. The simulation results showed that the design scheme of spade arm was feasible with structure, while the results of prototype test indicated that the structural design scheme of the spade arm was feasible. So the improvement scheme is basically feasible because the simulation results of the force and displacement on the spade arm are basically the same as the practical test results.