Abstract: By abstracting of solid parts in assembly level and assembly modeling based on the abstracting parts, product sym-bol assembly models are presented. Aiming at the qualitative features of conceptual product structures, by qualitative descri-bing of space position relations among parts in symbol assemb-ly models, the assembly qualitative models in concept design are presented. Assembly pair, symbol assembly relation, qualit-ative geometry constraint, qualitative geometry constraint graph are discussed and qualitative modeling examples are presented.

Key words: Assembly modeling, Concept design, Qualitative model