The work aims to divide the icon into two dimensions of structure complexity and information complexity to explore the associa-tion between icon semantics and information complexity and observe the differences between the two factors on the recognition accuracy and reaction time of elderly users, and then summarize the commonness of elderly users' interpretation, and find suitable icon design principle to make users get better performance. An icon recognition test was conducted for 30 elderly participants through experiment and in-depth interview method. By pairing icon and semantics, the impact of "structure complexity/information complexity" on recognition efficiency was explored. Information complexity was more important than structure complexity in de-termining icon recognition rate. Icon for the elderly should be designed with less than 14.5 bit information load. Under the same information load, "figure", "appliance" and "nature" should be used as the main elements, and "geometry", "letter" and "pointing" used as the auxiliary elements. The prototype of icon aided design system SIID1.0 is constructed, and the validity of the early in-formation complexity principle is verified through the evaluation of the design scheme.