Abstract: In order to design and define the geometric parameters in a shortcut efficiently for spatial RSSR mechanism, base on the analysis of motion characteristics for a specific RSSR mechanism, an integration method of diagrammatizing and 3D motion simulating has been introduced to obtain the geometric structural parameters. The simulation of 3D motion verifies the validity of presented method. It also shows the specific ways of adjusting the structural parameters to meet the required motion precision of the mechanism. The method described in this paper significantly improves the process of geometric parameter design for spatial RSSR mechanism and it could be used further in engineering practice.