A contactless method for determination of the parameters of the current-voltage (I—V) characteristic of hard superconductors by measuring the magnetization relaxation of the superconductor in a perpendicular magnetic field has been developed. The relaxation curves obtained for melt-textured YBCO samples are well approximated by the curves calculated within the electrodynamic model based on power-law I—V characteristics. This procedure uses only two fitting parameters: the critical current density J c and the exponent m of the I—V characteristic.