The invention provides a control device for residual current in a low voltage power grid, and comprises a residual current controller, a zero line grounding detector, an overvoltage detector, a zero-sequence current detection controller, a time controller, an actuating member controlled by the time controller, and a load switch controlled by the actuating member, wherein the zero line grounding detector, the overvoltage detector and the zero-sequence current detection controller are connected with the time controller, which comprises a time relay; and the residual current controller comprisesa potentiometer, a residual current relay, a closed contactor of the time replay in the time controller and a normally open contactor and a normally closed contactor of the residual current relay. The device has the advantages of scientific designing, low cost, high power supply reliability, and assurance of personal safety, and overcomes the shortcomings of the existing residual current protector, including frequently tripping and non-detectable line insulation during operation at the same time.