Based on the multilayer dielectric model, this paper presents an equivalent circuit model about pulsed electric field, which adapted to spherical bio-cells. In the same frequency domain, the variation tendency of intracellular membranes and epicyte are same, and spectral analysis shows that different frequency spectrum electric field can cause different biomedicine effect. This paper will introduce our work about how to calculate trans-membrane voltage and discuss the relationship among pulse, trans-membrane voltage and impedance, which indicates that different frequency domain and different duration have an effect on the selectivity of intracellular membranes and epicyte. Analysis of time domain and frequency domain shows that on the surface of the cell exists a window, when the duration is between 10^-8～10^-6 s, and the voltage of intracellular membranes will exceed the epicyte’s. The result also indicates as t increases, the outer and inner membrane field intensity decreases but bounce back when t is about 3.2×10^-7ns of parameters group, which means this is a minimum and is a very meaningful value for the following research. The Window Effect provides a research approach to accounts for biomedicine effect about electrical pulses.