This paper presents a "Global Learning Method" (G.L.M.) that can be used to construct a human-friendly interface for man-machine systems. The aims of the G.L.M. is to identify, in a user-friendly manner, the user's requirements of the environments by means of a fuzzy set in order to give adequate instructions to the machine to make a desired environment for the user. First, man-machine systems are considered from the viewpoint of human friendly interface. Second, the G.L.M. is proposed, and third, the method is applied to the practical problem of identifying the user's requirements in a color environment of the Graphical User Interface (GUI) of personal computers and the results are shown. Finally, the effectiveness of introducing the G.L.M. to the construction of a human friendly interface is discussed from the viewpoint of man-machine systems.