We investigate the entanglement of the ground state in the quantum cyclic graphs whose nodes are considered as quantum harmonic oscillators. To this end, the Schmidt numbers and entanglement entropy between two arbitrary partitions with equal nodes of a cyclic graphs, are calculated. For that, the local operation is used to build singular value decomposition of potential matrix of cyclic graphs. Then the maximum value of entanglement entropy among all bipartite cyclic graphs is obtained.
