The invention relates to dual laterolog equipment, an electrode system of the dual laterolog equipment and a formation resistivity measuring method. The electrode system comprises an electrode system body and an insulation core rod, consists of a plurality of electrodes arranged on one insulation core rod, and is connected with a measuring circuit through a conducting wire; insulation materials are used for separating the plurality of electrodes; the center of the insulation core rod is a metal rod; a through hole is formed in the center of the metal rod; the metal rod is isolated from the electrode system; the electrode system comprises main electrodes A0 and A0', at least one pair of shielding electrodes A2, A2', A1 and A1', a plurality of pairs of voltage measuring electrodes A1*, A1*', M0 and M0' and at least one pair of voltage monitoring electrodes M2, M2', M1 and M1', wherein the main electrodes A0 and A0' are arranged in the middle of the electrode system; the shielding electrodes A2, A2', A1 and A1' are used for emitting shielding current for focusing main current; the voltage measuring electrodes A1*, A1*', M0 and M0' are used for measuring electrode voltage; the voltage monitoring electrodes M2, M2', M1 and M1' are used for voltage monitoring; the shielding electrodes A2 and A2 are in short-circuit connection; the main electrodes A0 and A0' are in short-circuit connection; and other electrodes are not in short-circuit connection. Therefore compared with a hard focusing mode, the electrode system has high measuring precision.