Multi-loop coupled mechanism is a new kind of complicated mechanism which has been used in bio-robot, aviation, refuge and other areas. However, it is deficient in theoretical study. The most basic understanding for a new mechanism is to realize its mobility. Multi-loop coupled mechanism， i.e., serial-parallel hybrid mechanism, is different from the general parallel mechanism， and the former is coupled with each other among the branch chains．Therefore, the analysis of topology structure characteristic of multi-loop coupled mechanism is much more complex．Using the topological structure synthesis theory for parallel mechanism based on POC set and SOC unit ( POC method, for short)，the two classic multi-loop coupled mechanisms, symmetrical and asymmetrical ones, were analyzed. The correct degree of freedom and coupling degree could be calculated only if “coupling-number” was subtracted correspondingly by number of degree of freedom (DOF) and constrain degree when using the corresponding DOF formula and constrain formula．The coupling-number meant the coinciding number for over three branch chains, which was similar to the multiple-kinematic joint in the planar linkages. The result demonstrated that POC method can effectively analyze the multi-loop coupled mechanisms, and its physical and geometrical meanings were clear and the operation was simple and easy to understand. The structure of the multi-loop coupled mechanisms was seemingly complex，but its coupling degree was relatively low compared with 6-SPS Stewart-Gough platform with coupling degree of 3, and the kinematics and dynamic analyses were not complex．Therefore，the multi-loop coupled mechanisms have potential application value, and the application background still needs to be explored.