Dual Calorimetry is a technique designed for high precision control of detector calorimetry systematics. It is embodied in the JUNO experiment as two independent photosensors and readout electronics systems with different photon occupancy regimes surrounding the 20 kton liquid scintillator. One is the ~17,600 20-inch large PMTs (LPMTs) system, and the other is the ~25,600 3-inch small PMTs (SPMTs) system. The LPMT system is designed for maximal light detection in order to achieve 3% energy resolution at 1MeV. The SPMT system, as the second calorimetry, is introduced to disentangle the degeneracy of calorimetry responses, isolate the charge non-linearity effects and provide a linear charge reference for LPMT. The Dual Calorimetry technique provides precise control of LPMT charge measurement effects from reconstruction, calibration and monitoring aspects, thus helping the overall systematics control and physics measurement of JUNO. In this poster, the physics motivation and basic concept of Dual Calorimetry will be introduced. The novel Dual Calorimetry technique in terms of reconstruction, calibration and monitoring, together with its potential performance will be presented.