Due to the absence of defect-free blanks in extreme ultraviolet (EUV) lithography, defect mitigation is necessary before mass production. Currently almost all the defect mitigation methods are focused on mitigating the defect impact of one blank on one design. However, since the EUV mask vendors always have multiple designs and blanks in hand, it is also very important to consider all designs and blanks together to mitigate the total defect impact. This paper proposes a new EUV mask preparation strategy which optimally matches a set of defective blanks with multiple designs to mitigate the total defect impact. In the first step, an efficient layout relocation algorithm is adopted to minimize the defect impact of each blank on each design. Then, depending on whether blank defects are allowed to be compensated, we formulate the two different types of design-blank matching problems as flow problems and solve them optimally. Compared to sequential matching, the proposed simultaneous matching strategy shows advantages in both blank utilization and defect compensation cost minimization.