The Jiangmen Underground Neutrino Observatory (JUNO), a 20-kiloton liquid scintillator detector equipped with 17612 20-inch photomultiplier tubes (PMTs) and 25600 3-inch PMTs, is under construction currently, aiming to detect reactor, solar, atmospheric, geo neutrinos and neutrinos produced by a supernova collapse. To accurately achieve these multi-purpose physics goals, the detector energy resolution better than 3% at 1 MeV and the uncertainty of the absolute energy scale below 1% are required. In order to meet these stringent requirements, a comprehensive calibration system comprising the Automatic Calibration Unit, the Cable Loop System, the Guide Tube Calibration System and the Remotely Operated Vehicle is under development to calibrate the energy non-linearity and non-uniformity of the Central Detector (CD). This proceeding will summarize the design and development of the calibration subsystems, and report on their installation status.