From the perspectives of modularization disassembly, the influence of entity structure, function, motion and other factors of product brought to disassembly efficiency is elaborated. A way to improve design facing modularization disassembly is proposed. The time and cost of disassembly are checked by the proposed method through examples. Comparisons of disassembly evaluation before and after improvement are conducted based on the results. The general method to improve design is summarized. In terms of differences of repair probability of key parts in maintenance process, the improvement design criterion is put forward in the method, which improves the maintenance efficiency, reduces the maintenance cost and difficulty of disassembling operation and avoids data explosion of disassembly sequence because of too many parts.