Abstract: The reliable assessment of insulation state of oil immersed power transformer is related to the safe and stable operation of the whole power system. Owing to the advantages of convenient measurement, slight environmental interference, abundant insulation information, and strong sensitivity of insulation problems, the dielectric response characteristics of oil immersed power transformer are applied to the insulation state assessment of transformer by many experts and scholars at home and abroad and a lot of research work is carried out. The measurement method and principle of dielectric response characteristics are described, focusing on qualitative analysis of dielectric response curve with transformer insulation state, extraction of new dielectric response characteristic parameters and mutual fusion of multi-dimensional dielectric response characteristics. It points out the problems and shortcomings of existing research, and prospects the future research direction of the dielectric response characteristics in the transformer insulation state assessment according to the development of smart grid.