Abstract: The isolated power supply transformer is the core equipment for high-voltage DC circuit breaker to obtain energy, which transmits power from ground potential to the DC circuit breaker in high-voltage DC lines and ensures reliable and stable operation of DC circuit breakers. The 200 kV DC high-voltage isolating transformer introduced in this paper is made up of four 50 kV transformers. Due to the distributed capacitance, the rated DC voltage and the transient over-voltage of the pole line are unevenly applied to the four transformers, which increases the risk of insulation failure of a single transformer. In order to solve the above problems, we analyzed the circuit of the high-voltage DC isolation transformer, extracted distributed capacitor parameters, and completed the design and parameter configuration of the voltage equalization scheme. On this basis, voltage percent deviation of four-stage isolation transformer could be controlled within ±5% through equalization design, which was verified by simulation analysis and tests. The research results show that the voltage equalization method with 200 MΩ resistor and 1 nF capacitor in parallel can meet the engineering design and operation requirements of high-voltage DC isolation transformer.