Abstract: Green design emphasizes a product’s environmental character and looks it as a more important design objective in its whole life cycle，while modular design peculiarities are module-oriented and function analysis，in which series of products can be formed by modules’ selection and combination. By combining green design and modular design and importing the analytic hierarchy process，a methodology of green modular design is founded and its design flow is discussed. It can polymerize some parts into one by using the part-united rule and divide all parts into different modules by using functional rules and green rules. Furthermore，it also can ensure a product’s functional characters and environmental characters. Finally，an example of the outdoor set of a detached air-condition is given to validate and analyze the methodology.

Key words: Analytic hierarchy process, Function analysis, Green design, Modular design