The dynamic current-voltage characteristics of the micro-arc oxidation process were modeled by approximating the experimental curves. The hypothesis about the possibility of approximation of the anode ascending and cathode  incident branches by exponential functions due to the presence of a valve effect in the metal-oxide-electrolyte system is confirmed. The selection of approximating curves for sections of micro-discharges is performed. The correctness of the approximating functions choice was evaluated by determining the approximation error at the experimental points. It is shown that it is expedient to use a polynomial function for approximating sections of anodic  microdischarges, and an exponential function or a hyperbolic sine for sections of cathode ones. The limitations of the approach used in this work, which are associated with the approximate nature of the approximating functions, as well as with insufficient research into the mechanism of micro-arc oxide coatings formation are revealed. The simulation results can be used to develop a digital twin of the micro-arc oxidation process.