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The four degrees of freedom（DOF）SCARA parallel mechanism（PM）is widely used in industrial manufacturing since it has three translations and one rotation (3T1R) pose positioning function. In general, this kind of PM features complex structures, high coupling degree, no inputoutput motion decoupling and singularity etc. Firstly, according to the topological design theory of PM based on the position and orientation characteristic (POC) equations and principle of avoiding singularity by using redundant actuation limb, a new and symmetrical 3T1R partially decoupled PM with low coupling degree κ and a redundant actuation was proposed. Then the topological characteristic analysis of the PM was performed, including POC set, DOF, coupling degree and motion decoupling performance. Afterward, according to the kinematics modeling principle based on ordered single opened chain (SOC), the solution model of direct kinematics was established, and the position solutions of the PM were solved by using onedimensional search method. Then, the workspace and rotational ability of the PM were analyzed based on the inverse position solutions derived. At the same time, the geometric conditions of three kinds of singular positions were also derived and the principle of avoiding the singular position using redundant driving chain was explained. Meanwhile, the velocity and acceleration curve of the base point of moving platform of PM was simulated based on the derived formula. The research result laid a theoretical foundation for the mechanical design, prototype implement and application of the manipulator.