The invention provides a method for designing a double patterning. The method comprises the following steps: providing a decomposition patterning; performing collaborative light source mask optimization simulation on the decomposition patterning to obtain a hot spot region for limiting an overlapping process window; adjusting the size and/or the spacing of a patterning in the hot spot region and performing collaborative light source mask optimization simulation to eliminate the hot spot region; adding the size and/or the spacing of the set patterning when the hot spot region is eliminated to a rule base to obtain an updated rule base; splitting a patterning which at least comprises a patterning part in the hot spot region according to splitting rules in the updated rule base to obtain a hot spot region decomposition patterning; updating the hot spot region decomposition patterning to an original decomposition patterning to obtain an updated decomposition patterning. The method is used for splitting optimization during the design process, so that repeated splitting caused by the design defect generated by improper pre-splitting is avoided, the design is simplified, and the design efficiency is improved.