Abstract: In order to study the internal temperature distribution and the corresponding insulation performance of the epoxy resin impregnated paper bushing, a synchronous test circuit for temperature rise and insulation performance of the bushing core was constructed. And the temperature distribution and effects of the hottest spot temperature on the insulation performance of the bushing under different currents were obtained. The results show that local hot spots may be caused by heat accumulation at the maximum diameter of the core at the bushing oil end under current carrying conditions. When the hot spot temperature in contact with the insulating material of the bushing is lower than 100 ℃, the phenomenon of relaxation polarization loss is obvious. There are "peak" and "valley" in the tanδ- frequency curves, and the curve shifts to the high frequency direction with the increase of temperature. When the hot spot temperature is higher than 120 ℃, the conductivity loss is prominent, and the tanδ-frequency curve shows a linear downward trend in the logarithmic coordinate system. If the hot spot temperature exceeds 140 ℃, the insulation of the bushing will be damaged, which is embodied in tanδ and the capacitance increases sharply, and the insulation resistance decreases significantly. In case of severe local overheating with hot spot temperature exceeding 200 ℃, a large amount of gas will be generated inside the bushing, and the core will crack. And the tanδ increase but the electric capacity decrease suddenly. This study can provide a reference for the optimal design, test and operation state evaluation of the bushing.