Induced voltage and current will be caused in conductors by irradiation of electromagnetic pulse（EMP）.It is significant to fully understand the propagating characteristic of EMP. Taking the high altitude electromagnetic pulse（HEMP）as an example

the environment on the ground and underground have been calculated by using the standard waveforms in IEC-61000-2-9—1996. It is can be seen that for the field on the ground

the reflection of the earth reduces the horizontal field

but increases the vertical field. The HEMP environment on the ground is far different from that underground. The earth parameters have a greater effect on field underground than the field on the ground. The magnitudes of field on the ground are much higher than those underground

especially for the vertical fields. The more the earth permittivity is or the smaller the earth conductivity is

the more the field mag-nitudes are. Angles of incident field are the random factors to the EMP environment.