In this paper, a new reconfigurable parallel mechanism by applying a spatial multi-loop over-constrained mechanism is proposed. The reconfigurable parallel mechanism has 4 degrees of freedom (DOF), and its different performance indices can be continuously changed. According to its inverse kinematic model, its workspace, dexterity, and stiffness are all analyzed. This paper also establishes the dynamics model, and a novel dynamic index is proposed to optimize the proposed mechanism. With these novel performance indices, both the kinematic and the dynamic performance for this mechanism are shown to be greatly improved.