A disassembility assessment has mostly depend on the subjective decision making from the qualitative element. The work of disassembly is already classified with given disassemble points from the symbolic chart method. It is not useful in the practical assessment because it is not specified. The new method of design for disassembility assessment(DFDA) is practical to introduce the fuzzy number as the conversion of quantitative element from qualitative. It is appled to air-cleaner of passenger-vehicle for the usefulness.