It studies the formation mechanism，features and design concepts of "Paradoxity" in ambiguity design. Based on the theory of symbolic interaction， it established the human-machine interactive model of devices information and users interpretation，made theoretical and application analysis of "Paradoxity" in ambiguity design. The ambiguity design is different from usability， Norman concept model， fuzzy design and design fault. "Paradoxity" is a critical point to define the interactive quality and category of ambiguity as the extreme condition between devises and users in ambiguity interaction.