[en] Based on the evolution of new publications by the International Commission on Radiation Units and Measurements (ICRU), the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the International Commission on Radiological Protection (ICRP), this paper reveals new progress of the ionizing radiation quantity system, radiological biological effects and radiological protection system which form the basis of radiological protection discipline. Thus it can grasp the development trend of radiological protection field. The fourth part of this article reviews the new progress of medical exposure protection, and it is closely related to all the public in the field of radiological protection. (author)