A method for generating a layout pattern is provided. First, a layout pattern is provided to a computer system and is classified into two sub-patterns and a blank pattern. Each of the sub-patterns has pitches in simple integer ratios and the blank pattern is between the two sub-patterns. Then, a plurality of first stripe patterns and at least two second stripe patterns are generated. The edges of the first stripe patterns are aligned with the edges of the sub-patterns and the first stripe patterns have equal spacings and widths. The spacings or widths of the second stripe patterns are different from that of the first stripe patterns.