Dielectric loss factor serves as a pivotal indicator for assessing the insulation effectiveness of converter transformers. Given the intricate operational environment of converter transformers, especially amidst DC power transmission, the internal oil-paper insulation structure remains susceptible to the ambient temperature, thereby instigating variations in the dielectric properties of the oil-paper insulation. Such fluctuations can potentially trigger operational malfunctions within the converter transformer. Hence, a comprehensive examination of influence on the converter transformer by temperature becomes imperative. In this context, exploring the impact of transformer oil and oil-impregnated pressboard on dielectric properties emerges as a matter of profound significance. This study thus focuses on employing the dielectric loss factor as the principal parameter for characterizing the dielectric properties of oil-paper insulation. By delving into the variations in dielectric loss factors across different temperatures, this paper investigates three distinct types of transformer oil and oil-impregnated pressboard, thereby shedding light on their respective dielectric behavior under varying thermal conditions.