The invention discloses a variable-ratio magnetic potential comparison type transformer calibration system capable of self-calibration. The variable-ratio magnetic potential comparison type transformer calibration system comprises a magnetic potential comparison unit and a sampling adjustment unit, wherein the magnetic potential comparison unit comprises a standard input winding W0, a detected input winding Wx and a magnetic potential balancing core T; the magnetic potential comparison unit is used for inputting currents to a standard current transformer T0 and a calibrated current transformer TX, so as to generate secondary currents I20 and I2X separately; the secondary current I20 is input to the standard input winding W0, and the secondary current I2X is input to the calibrated input winding Wx, so as to generate magnetic flux on the magnetic potential balancing core T; the sampling adjustment unit comprises a detection winding WJ, an in-phase compensation winding WF, an orthogonal compensation winding WD, an adjustment conductor G, an adjustment capacitor C, and amplification control circuits D1 and D2; and the sampling adjustment unit is used for detecting unbalanced magnetic flux on the magnetic potential balancing core T, and balancing the magnetic flux on the magnetic potential balancing core T through amplifying compensation currents ID and IF output by the amplification control circuits D1 and D2.