The high voltage arm resistance is a key factor to test accuracy when using a resistive divider as a voltage converter to measure high voltage which contain static and dynamic step, and the high measurement accuracy of the signal is an important indicator of the highvoltage test. This paper proposed the lowrated power resistor formed a divider to improve the accuracy of voltage test, and analyzing temperature changes under different cooling mode and different insulating medium. The issue of high temperature when selecting a low resistance be solved by reducing the initial temperature of resistance through active cooling. The experimental results show that the voltage measurement accuracy optimized effectively by using the lowrated power resistor which solved the problem of high temperature.