An optical proximity correction method is provided. A target pattern is provided, and then the target pattern is decomposed to a first pattern and a second pattern. The first pattern and the second pattern are alternately arranged in a dense region. Then, a compensation pattern is provided and it is determined whether the compensation pattern is added into the first pattern to become a first revised pattern, or into the second pattern to become a second revised pattern. Finally, the first revised pattern is output onto a first mask and the second revised pattern is output onto a second mask.