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Exechon parallel kinematic machine (PKM) has been applied to machining, assembling and aerospace industries due to its high rigidity and high dynamics. However, its rotational ability is comparatively weak. In order to improve the rotational ability of the Exechon PKM, an Exe-Variant PKM was proposed whose topology was a 2RPU&1RPS parallel mechanism. And the mechanical structure of the proposed Exe-Variant PKM was designed. In order to achieve a thorough understanding of stiffness characteristics of the Exe-Variant PKM, the stiffness model of the parallel module was designed by substructure synthesis technique. According to its structure feature, the Exe-Variant PKM was divided into several subsystems, including a moving platform subsystem, three limb subsystems and a fixed base subsystem. Meanwhile, the elasticity of joints and limbs was considered. Based on the proposed stiffness model, the stiffness distributions throughout the workspace were discussed and the parameters analysis on the stiffness of an Exe-Variant PKM was conducted. Results showed that the stiffness distributions of the Exe-Variant PKM were symmetric about a certain plane throughout the workspace, and the key design parameters had a great influence on the rigidity of the Exe-Variant PKM. Furthermore, the elastic deformation of joints seemed to have a greater influence on stiffness in z direction than those in x and y directions of the Exe-Variant PKM. It was worthy to point out that the analysis conducted can provide theoretical foundation for structure optimization.