With the increase in living quality and self-awareness, customers consider not only economic factors, but also personal requirements while making purchasing decisions. In addition to expertise in design, designers must consider the key factors that influence designing to face the change of consumer demands and the competitiveness of the craft. This study adopted the Modified Delphi Hierarchy Process (MDHP) method to establish an index in apparel design. First, this study established the index in apparel design by the Modified Delphi method of expert questionnaires to sift the design guidelines that are commonly agreed upon. Next, the Analytic Hierarchy Process (AHP) method was applied to conduct professional evaluations and obtain relative weights of indicators under the examination of inconsistency assessment. Study results show that the top three design indices are the application of design guidelines, understanding of fabrics, and artistry and esthetics. Based on this design index, we can attain crucial references in apparel design and development.