Cyclic polymers with ring topology and no chain ends are a unique class of macromolecules. Recently, significant advances have been made to prepare these fascinating polymers, which allow for the exploration of their topological effects and potential applications in various fields. In this talk, I first show representative synthetic strategies for making cyclic polymers. Second, I will show examples application of cyclic polymers to nonbonding cross-linking agent for polymer network with movable cross-linking points. Recently, new approach for constructing polymer network has been developed utilizing mechanical cross-linking through chain threading of ring segment. These network polymers are expected to exhibit good swelling properties and high impact strength due to high degree of freedom in the segmental movement since cross-linking points can move. One methodology to introduce such movable cross-linking points is to carry out copolymerization of cyclic macromonomer with a monomer. Chain threading of the cyclic segment by the propagating main chain leads cross-linked structure. However, drawback of this method is that network structure is not homogeneous. Because network structure forms at early reaction stage and the viscosity of reaction mixture increases rapidly, so, diffusion of cyclic macromonomer becomes difficult. Therefore, we designed two-step cross-linking method. First step is formation of pseudopolyrotaxane. And second step is covalent fixation of ring segment to linear segment. We applied this two-step cross linking strategy for preparations of hydrogel and silicone with movable cross-linking points.