This paper is focused on the performance analysis of a newly developed 6-DOF Parallel-Kinematics Machine (PKM). The design related analysis issues such as the instantaneous kinematics, manipulability, accuracy, and stiffness are addressed. This new PKM has three identical RPRS legs to support the moving platform. Since all joint axes, excluding the three spherical joints at the leg-ends, are parallel to each other and perpendicular to the base plane, this 6-DOF 3RPRS PKM exhibits decoupled motion characteristics such that translation along the vertical direction and rotation about horizontal axes are only driven by the three active-prismatic joints, while translation in horizontal planes and rotation about vertical axes are mainly driven by the three active-revolute joints. The PKM also has a large cylindrical reachable workspace and high stiffness in vertical directions. These features make it a promising 6-DOF machine structure for light machining and heavy parts assembly tasks.