Abstract: For the problem of ELF electromagnetic wave propagation in layered medium with target body,remaining in controued-source electromagnetic method (CSEM)forward calculation,a method based on "disturbance" and Green functions is put forward.This method regards the electromagnetic fields in target body directly as the source of the second-fields at the receiving points,and combines Dyadic Green functions to calculate the fields without solving matrix functions.Results show that if the target body can be regarded as "disturbance" compared with the background medium,the precision is acceptable.Finally,2-D pictures about electric amplitude distribution which gained by method based on "disturbance" and Green functions are given with target body at different locations.In the pictures, the effect of body location on its work region can be seen clearly,which provids proof for inversion.