The invention provides a horizontal detecting device, levelling device and levelling method of a workpiece in an electrochemical system. The horizontal detecting device comprises a macrometric/micrometric displacement platform, a displacement table, a probe electrode and an electrochemical workstation. The displacement table is fixedly arranged on an X-Y plane which is determined by the macrometric/micrometric displacement platform and can make displacement on the X-Y plane, and an electrolytic tank and the displacement table are relatively static. The probe electrode is fixedly arranged in a Z direction which is determined by the macrometric/micrometric displacement platform, and the detection end of the probe electrode is soaked into an electrolyte in the electrolytic tank in a vertically downward mode and is away from the workpiece in the electrolytic tank by a preset distance. The working electrode of the electrochemical workstation is connected to the probe electrode, the auxiliary electrode and the reference electrode of the electrochemical workstation are both connected to be soaked into the electrolyte in the electrolytic tank, the potential of the working electrode is controlled to be constant, current signals of the working electrode are changed along with the movement of the displacement table, the current signals are detected, so that a current signal curve is obtained, and the tilting degree of the workpiece in the electrolytic tank can be known through the fluctuation amplitude of the current signal curve. By means of the horizontal detecting device, levelling device and levelling method of the workpiece in the electrochemical system, the horizontal detection precision of the workpiece in the electrolyte can be improved.