The article is devoted to the problem of calculation the value of current of non-self-sustained arc discharge, which is lighting and maintained in the metal vapours and active gases for porviding the chemical reaction between its in the technological process of evaporation of thin coatings. Obtaineed relations are generally based on Poisson equation for defining the distribition of electric field, Mendeleev – Clapeyron equation for defining the concentration of ions in saturated metals' vapours, as well as on equation of current continiouty in gas discharge. Formed set of equations for distribution of electric potential and discharge current in the spatial coordinates is transformed to cubic equation, which was solved analytically. Obtained simulation results are given and analyzed.