The present invention provides a method of forming tight-pitched patterns. First, a target pattern is provided, wherein the target pattern comprises a plurality of first stripe patterns, and each of the first stripe patterns has a first width and a first length. Then, a photomask comprising a plurality of second stripe patterns corresponding to the first stripe patterns is provided, and each of the second stripe patterns has a second width and a second length. Then, a first exposure process with the photomask is provided in an exposure system, wherein the first exposure process uses a first light source that can resolve the second width of each of the second stripe patterns. Lastly, a second exposure process with the photo-mask is provided in the exposure system, wherein the second exposure process uses a second light source that cannot resolve the second width of each of the second stripe patterns.