The current transformer converts the large current in the primary system into a small current for secondary measurement and measurement protection in the power system. It plays an indispensable role in the stable operation and fault current measurement of the power system. However, during the online operation process, the abnormal increase in gas of the oil inside the transformer induced by partial discharge, heat failure, etc. will lead to sharp increase of the internal pressure, which will easily cause insulation damage and explosion. In order to study the internal temperature field distribution of the transformer and the influential factors of pressure changes so as to detect the internal pressure surge failure in time, a model of 220 kV inverted oil-immersed current transformer was established by ANSYS software simulation. Based on the model, the distribution law of internal temperature field of the current transformer was obtained by finite element analysis method. An experimental platform was established to verify the validity of the simulation. At the same time, an online pressure monitoring system based on MD-TPR transformer was designed, and the internal pressure influence characteristics of the transformer were obtained.