The invention discloses a single-phase insulated electric fire on-line prevention and control device and a method thereof, include a control output unit, single chip microcomputer module, DSP unit, aresidual current signal detection and conditioning unit for detecting and conditioning a lumped residual current signal in a protected single-phase AC loop in real time and a voltage signal detectionand conditioning unit for detecting and conditioning a phase voltage signal in the protected single-phase AC loop in real time, wherein the output terminal of the residual current signal detection andconditioning unit and the output terminal of the voltage signal detection and conditioning unit are connected with the input terminal of the DSP unit, The output end of the DSP unit is connected withthe input end of the single chip microcomputer module, and the output end of the single chip microcomputer module is connected with the control output unit. The device and the method can on-line monitor the insulation performance of the single-phase alternating current loop, on-line identify the potential electric fire hazard, and effectively prevent the occurrence of the short-circuit fault andthe electric fire accident.