The precise measurement of the Higgs boson mass is crucial in understanding the fundamental properties of our universe. In the context of Higgs decay into two photons, the accuracy of the electromagnetic calorimeter’s calibration plays an important role. To achieve outstanding precision in photon energy, extensive works have been made to refine the full chain of photon energy calibration and minimise the associated uncertainties in ATLAS experiment. Moreover, a novel method has been employed to constrain the energy-dependent systematic uncertainties by using data-to-MC energy scale difference observed in Et bins with Z->ee events. These advancements have resulted in unprecedented accuracy in photon energy measurements. Consequently, this has contributed to the latest Higgs boson mass measurement in the diphoton decay channel, further advancing our understanding of the Higgs boson properties.