The calibration of absorbed dose of medical electronic linear accelerator is one of the most important contents of radiotherapy quality control. In particular, the widespread application of precision radiotherapy puts forward higher requirements for the accuracy of radiotherapy dosimetry. Compared with the absorbed dose dosimetry procedure based on calibration factor in terms of air kerma/exposure, the advantages of the absorbed dose dosimetry based on calibration factor in terms of absorbed dose to water are: reduced uncertainty, no quantity conversion factors, simpler physical concept and simpler calculation formula, etc. According to relevant existing standards, this guideline specifies the dosimetry procedures and relevant requirements for high-energy beams of medical linac based on calibration factor of absorbed dose to water, provides guidance for domestic medical institutions to determine the absorbed dose of high-energy photon and electron beams, and provides support for the development of precision radiotherapy.