Abstract: Based on the detection and orientation of the broken point of the cable buried in the seabed, the cable is considered as finite-length linear electricity source.From the Maxwell function and boundary condition, the integral expressions of the electromagnetic field in the planar layered medium including the atmosphere, the seawater layer and the rock layer are derived.The field excited at different observation points by the cable are analyzed by numerical integral.The direction of the cable and the position of the broken point can be estimated via the characteristics of the magnetic field around the broken point on the sea.