Research conclusions: The calculation of the magnetic response of long wire source could be realized by splitting the long wire source into multiple dipoles with Hankle transform．When doing calculation of the magnetic response of long wire resource，the long wire source could be splited into multiple electric dipoles according to the distance of sender， receiver and the wire length．Then the electric field and magnetic field in level direction on the ground generated by the multiple electric dipoles were calculated with Hankle transform，and the magnetic responses of every electric dipole was Sided to obtain the response of the long wire source．The verification showed the results of some classic models excited by long wire source were right and meaningful to the inversion of CSAMT．