A method of performing optical proximity correction for preparing a mask projected onto a wafer by photolithography includes the following steps. An integrated circuit layout design including a first feature and a second feature is obtained, wherein the first feature overlaps a first boundary of two structures in the wafer. An edge of the first feature close to the second feature pertaining to a specific trend section of an experimental chart having trend sections is recognized. An optical proximity correction value is evaluated for the edge through a computer system according to a rule corresponding to the specific trend section. The layout design is compensated with the optical proximity correction value.