The Madelung constant can reflect the physical properties of crystals, but its calculation by conventional methods is quite cumbersome. To simplify the calculation of the Madelung constant, a new method based on unit cell nested structure has been developed. Matlab plotting was used to illustrate the formation process of nested unit cells and the distribution pattern of outer ions in two-dimensional hexagonal ionic crystals at various levels. It was found that, according to the number of positive and negative ions in the crystal and by eliminating boundary effects, the ionic crystals at various levels are electrically neutral. Moreover, based on the distribution pattern of outer ions, a recursive formula for calculating the Madelung constant using the nested unit cell-outer Ewald method was derived. The Madelung constant of multi-level two-dimensional hexagonal ionic crystals was calculated using the iterative method, resulting in a simple approach for calculating the Madelung constant of crystals.