Addition of EDTA to the KDP solution is an effective method to increase the stability zone and the crystal growth rate. EDTA neutralizes the chemical activity of metal ions impurity such as Al⁺³, Fe⁺³, Cr⁺³ (that exist in the chemical materials as impurity). Effect of Al⁺³, Fe⁺³, Cr⁺³ ions on the KDP crystal is investigated. Growth method was based on the “point seed” method following spontaneous growth at room temperature in a solution with optimum concentration. UV-Visible spectrum of the crystal containing Al³⁺ displays an undesirable increase of the optical absorption in the ultraviolet region. In fact, (AlO₄)^2- ions are present in the KDP crystals and give rise to ultraviolet absorption. Addition of EDTA to the KDP solution lead to decrease the optical absorption in the ultraviolet region and equal growth rate at all faces of the crystal.