The measurement of corona discharge current is an important research indicator, and there is little analysis of the spatial distribution of corona current. This article proposes an approximate analytical calculation method for the displacement current in plate electrode corona. Firstly, a simplified calculation model was proposed, and two sources of displacement current were derived: net charge change and net charge motion in the streamer head; Secondly, two calculation formulas for displacement current density and port displacement current formed by electric field changes were provided, and their variation patterns were analyzed; Finally, the results and conditions for generating reverse displacement current density on the same electrode plate are presented, which are controlled by the gap and plate electrode radius; The issues of electrode size setting in experimental measurements and boundary condition setting in numerical simulations were also discussed. The above results can provide theoretical guidance for accurate measurement and analysis of corona current.