Abstract: To scientifically and practically measure the ionizing radiation in unison is an indispensable prerequisite and foundation for the extensive uses of nuclear science and technology, development of radiological protection and safety standards, as well as prevention and treatment of ionizing radiation hazards. Concerning about the quantities and units of ionizing radiation as well as their corresponding measurement and application methods, relevant international organizations and all countries in the world generally adopt the systems proposed by the International Commission on Radiation Units and Measurements (ICRU) which is a well recognized and authoritative academic organization. In the paper, the major evolutions of the systems for ionizing radiation quantities and units in the past decades are summarized.