The Jiangmen Underground Neutrino Observatory (JUNO) is designed to primarily measure the neutrino Mass Hierarchy. Its Central Detector (CD) will be the largest liquid scintillator (LS) detector to measure the energy of neutrinos with an unprecedented energy resolution of 3% @1MeV and an energy nonlinearity better than 1%. Accordingly, a calibration complex is designed for multiple source deployment, the energy coverage of reactor neutrinos and CD full-volume coverage. In this proceeding, the design details and primary progress about JUNO calibration system are presented.