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The theory of degree of freedom (DOF) analysis for multiloop coupling mechanisms is not yet mature at present. Aiming at the DOF analysis of a spatial multiloop coupling hexahedron deployable mechanism, a method was presented based on the idea of selecting a hypothetical moving platform, establishing the equivalent series supporting limbs, constructing the equivalent parallel mechanism (PM), and then analyzing the DOF of the equivalent PM to obtain the original hexahedron mechanism. One of kinematic chains composed of more than one link was selected as the moving platform at first, and all kinematic equivalent series supporting limbs of the moving platform were established based on the screw theory. Then the number of links contained in the moving platform was reduced continuously, and the equivalent series limbs were reestablished. The original hexahedron mechanism was eventually equivalent to a traditional PM whose moving platform consisted of just one link. The number and properties of the DOF of the multiloop coupling hexahedron mechanism were obtained by analyzing its equivalent PM. The coupling degree of the hexahedron mechanism was reduced by the proposed method, so that the difficulty of DOF analysis of the original multiloop coupling mechanism was reduced. In addition, the simulation model of the hexahedral mechanism was built, and the kinematic characteristics of the mechanism were studied by giving different actuations. Furthermore, the folding performance of the mechanism was discussed. The research results of DOF and kinematic characteristics laid a foundation for the force analysis of the hexahedron mechanism, and the proposed method provided a way for the DOF analysis of other types of polyhedron mechanisms.