This paper presents a calculation method of the step response of resistive voltage divider by transient electric field theory. Practical calculation is made on a 1.5 MV resistive voltage divider.The calculation results demonstrate that the method can provide a general conception of the transient behavior of a voltage divider under a step voltage and can evaluate the divider characteristics for measuring impulse voltage. This method is a useful tool in design and optimization of resistive voltage divider.