產品設計是一項整合藝術、科技與經濟資訊於一體的創造性活動，其最終目標旨在完成一項滿足人類生理與心理需求的產品。然而人類的思想、行為及語言本身就具有高度的模糊性，對於產品的需求或是滿意程度，常以概括的意象語彙來表示。在傳統的設計過程中，設計師在面對這些模糊不清的意象語彙時，大都根據其個人的經驗、喜好、習慣與靈感，從眾多的設計構想中，主觀的選擇出其認為理想的設計方案，在這種缺乏理論依據的決策模式下，實在很難確實而有效的獲致真正符合消費者需求的產品。本文主要以座椅的設計為例，利用模糊理論中的加權平均法與廣義加權平均法，由使用者的語意調查開始，透過電腦化的輸出入界面進行模糊運算，建立一套多層級的模糊決策模式，將設計師所面對的模糊意象做量化處理，使設計師能根據這些量化的結果進行設計方案的選擇。此一模式的建立，可達到多方面而客觀的綜合評判，不僅可以降低決策失誤的機率，更可提高決策的效率，並增加新產品開發成功的機會。雖然文中僅以層屬架構較為簡單的座椅設計為例，說明設計決策的執行程序，然而它可更進一步應用於其他更複雜產品的設計。

　　　　　Product design is an activity synthesized with art, technology and economics whose objective is to get a product satisfying the physical and psychological demands of human beings. However, the thought, behavior and language of human beings are full of fuzziness. The demands and degree of satisfaction that a person has with a product are usually represented with image words. Traditionally, the best design is subjectively selected from design alternatives based on designer's experience, delight, habit and inspiration when a lot of image information are faced. It is difficult to get a product satisfies, the customer’s demands with a decision model of that lacks of theoretical support. In this article, the design of a chair is taken as an example to construct a fuzzy decision model for a system with multi-level factors. Computerized questionnaires are used to get user’s psychological responses to each part of the chair, which are then converted, into the membership functions. The weighted mean and weighted generalized mean methods for fuzzy operations are used to quantify the fuzzy images. After comparing the membership grades of the design alternatives, the optimal design can be selected by the designer. With this decision model, not only can the error of a design decision be reduced, but the efficiency of the decision-making can also be improved. In addition, this decision model can further be used to design other more complicated products.