We obtained a relation between the characteristics of optical life and panel structural factors which is one of the important factors for panel design of Plasma Display Panel (PDP). We introduced the equation under the consideration that dominant factor determining the characteristics of optical life is luminance degradation of phosphors and that ion bombardment causes luminance degradation of phosphors. This equation contains the following four panel structural factors such as gap between electrodes, gas pressure, gas kinds, and voltage. Furthermore, we compared the equation with experimental values as a verification.