The invention provides a method for simulating electromagnetic distribution conditions in a simulating strong electromagnetic pulse environment. The method comprises the following steps of simulating electromagnetic pulse waveform under a time domain by using a hyperbolic cosine function; performing simulation on change of electromagnetic fields of the environment by using a time domain finite difference algorithm; implementing acceleration of the time domain finite difference algorithm by using a GPU (ground power unit) to obtain electromagnetic distribution conditions on the time domain; and obtaining the electromagnetic distribution conditions on a frequency domain through fast Fourier transform. By the method, distribution characteristics of the electromagnetic environment of an ultra-electromagnetic large-size object can be implemented when the ultra-electromagnetic large-size object is attacked by electromagnetic pulse weapons.