Development and practical application for practical parallel mechanisms still have a long way to go, the reason is that the topological structure characteristics of the mechanisms are to be revealed. The purpose of topological structure characteristics analysis is to provide criteria for optimization and performance assessment of parallel mechanisms. Using topology structure theory for parallel mechanism based on position and orientation characteristics (POC) and the ordered single-open-chain (SOC), the topology characteristics of six practical and useful parallel mechanisms were analyzed, and three main topological structure characteristics, including the POC set, degree of freedom (DOF) and coupling degree were uncovered. Analysis for topological structure characteristics was an effective method to reveal the structure composition and the topological structure characteristics of mechanisms. The best structural decomposition route can be achieved with the concept of “coupling degree”, the complexity caused for forward kinematic analysis of the mechanisms can be reduced and the forward position solutions of mechanisms can be analyzed efficiently. These characteristics reflected the basic performance of the topological structure, kinematics and dynamics of these mechanisms, which provided theoretical foundation for the optimization of topological structure, kinematics and dynamics as well as application. Topological structural analysis of practical parallel mechanisms can provide comparable schemes for innovative mechanism designs. This work also revealed some general rules which can be beneficial to the design and application for any other parallel mechanisms.