The utility model discloses a three-current-mutual-inductor control device for performing online monitoring on multipoint grounding current of a transformer clamping member, and solves problems in the prior art that normal operation of a power grid is influenced by a mode of operation of power outage and current limiting on the transformer clamping member. A clamping member grounding lead-out wire (9) penetrates through a coil of a first current mutual inductor (10) and is connected with an input end (21) of a switching circuit. The two ends of secondary side sensing coils of the three current mutual inductors are respectively connected with two input interfaces of an AD conversion interface circuit. The output end of the AD conversion interface circuit (15) is connected with a single-chip microcomputer (17). The output end (22) of the switching circuit is connected with a grounding end (6). Impedance units of three switching branches acting as current-limiting impedance units adopt bidirectional thyristors to control on/off of the branches. With control of conduction angles, on and off of the impedance branches can be controlled and switching of the impedance units can be realized. The device is high in operability so that normal and safety operation of the power grid is guaranteed.