Electrostatically driven membrane deformable mirrors correct wavefront aberrations through electrostatic forces, whose correction capability dependent on driving load accuracy. Due to the charge aggregation at the electrode edges, non-uniform deformation occurs due to the nonlinear change of the regional load, which causes inaccurate or incorrect assessment of the calibrated wavefront aberration of electrostatically driven membrane deformable mirrors. Based on this, this work carries out a study on electrostatically driven membrane deformable mirror electrode edge effect and its influence on correction capability assessment, establishes a theoretical model of electrode edge effect, and quantitatively analyzes the influence of electrode edge deformation response and correction capability assessment accuracy based on the model, and the results show that before and after the consideration of the edge effect, the error of correction capability assessment is improved from 25.49% to 6.83% or even lower, and applies to different electrode spacing parameters, which verifies the correctness of the theoretical model proposed in this paper.