Abstract: A device and method for geo-electric extraction under water layer coverage are provided. The device includes auxiliary tubes, outer casings, main tubes, mud extractors, encapsulated extraction electrodes and a fixing ferrule assembly, where the auxiliary tubes each have one end open and the other end closed; the outer casings each have one end open and the other end detachably connected to a top cover; an inner diameter of each of the outer casings is larger than an outer diameter of each of the auxiliary tubes; an outer diameter of each of the main tubes is smaller than the inner diameter of each of the outer casings; the mud extractors each include an inner rod, an outer rod and a bottom plate; the outer rod is sleeved outside the inner rod; the inner rod has one end provided with a dredging wheel and the other end provided with a handle.