This paper attempts to apply the Schwarzschild metric of the gravitational field to the electromagnetic field to obtain a Schwarzschild radius in an electromagnetic field. According to this radius, microscopic space-time can be divided into two parts, the real space-time outside the radius of the electromagnetic field Schwarzschild, and the virtual (or imaginary) space-time within the radius. The properties of these two space times are exactly similar to the space time features inside and outside the radius of the event horizon in gravitational black holes. Combined with virtual space time-based particle models and the latest experimental data on proton electromagnetic radius, we can calculate a more accurate proton-to-electron mass ratio.
