A method to compensate optical proximity correction adapted for a photolithography process includes providing an integrated circuit (IC) layout. The IC layout includes active regions, a shallow trench isolation (STI) region and ion implant regions overlapped with a part of the STI region and at least a part of the active regions. Subsequently, at least a photoresist line width compensation region disposed in the STI region is acquired in a photoresist covering region outside the ion implant regions according to the IC layout. Afterwards, the IC layout is corrected according to a width of the photoresist line width compensation region, a length of a side of the active region facing a side of the photoresist line width compensation region and a distance from the side of the photoresist line width compensation region to the active region facing the side. Then, the corrected IC layout is transferred to a photomask.