A method and system for electromagnetic method (EM) signal detection based on an onshore sparker source, the method including: arranging an EM signal detection system near a sparker source; releasing, by the sparker source, an electromagnetic pulse concomitantly in a discharge and mechanical energy output process; observing an electromagnetic response generated by the earth under the excitation of the electromagnetic pulse by means of the EM signal detection system for extracting distribution information of geo-electrical parameters; when the sparker source moves, moving the electromagnetic method signal detection system to a new position along with the sparker source while keeping their positions relative to each other unchanged; and repeating the above process after the movement is completed. According to the technical solution of the present invention, fine electromagnetic detection results can be obtained while seismic detection is carried out.