There is a lack of clear correspondence between the existing icon semantics and design elements, which leads to the difficulty for elderly users in identifying icon semantics due to their lack of mental ability. To balance the “ability” of icon identification of elderly users and the “challenge” imposed by the product, and to build a bridge of icon identification and communication between designers and elderly users, and, based on the flow theory and the ability and demand matching gradient model, household appliance icons were classified and collected according to the cognitive mode. In the later stage, the semantic cognitive ability evaluation test was carried out for elderly users, and the relationship between user ability and icon cognitive efficiency was elaborated. An “ability-demand” matching gradient model is constructed for elderly users, and the effectiveness of the gradient is verified by the icon design evaluation of “hand wash mode” of a washing machine. With the requirement of design diversity, excess region of actual capacity can be selected preferentially in icon designing. A proper preference of in-capacity regions provides the elderly with more diverse designing options. Inadequate region should be avoided.