This paper outlines a systematic design methodology for mechatronic systems, which formalizes subjective notions and simplifies the optimization process, in the hope that communication between designers with various backgrounds and clients is enhanced and numerous design variables with different natures can be considered concurrently. The methodology redefines the ultimate goal of design based on the qualitative notions of wish and must satisfaction, and formalizes the effect of designer's subjective attitude in the process, which can be adjusted based on the reality of system performance. © 2008 IEEE.