Abstract: In order to explore the potential transmission capacity and maximize utilization of the power circuit, it is necessary to evaluate the dynamic thermal rating of the key power equipment in the power circuit. The dynamic thermal rating assessment of oil-immersed power transformers can maximize its dynamic load capacity, improve the utilization rate of transformers and enhance the observability of dynamic thermal rating of power circuit. By analyzing existing problems of the dynamic transformer rating applications, the paper discussed the typical application scenarios of dynamic transformer rating, and illustrated the key technologies, including deriving typical daily loading curves and ambient temperature curves, identifying hot spot temperature, evaluating insulation life and thermal condition assessment, and etc. The calculation process of transformer dynamic rating and its application examples were then described in detail. Finally, the characteristics and limitations of the practices of the dynamic thermal rating assessment technology for oil-immersed power transformers were discussed from the aspects of hot spot temperature identification, the correlation law between thermal aging and dynamic thermal rating, and the comprehensive evaluation of load capacity, and the future research direction was pointed out for researchers and engineers.