Abstract This paper investigates the theories and application of modular fixture design automation. Under the guidance of the theory of generalized mapping,a top-down fixture design automation software hax been developed. On the analysis of the fixturing characteristics of workpiece, the design requirement is extracted. The process of Function-Form Mapping relationship is comprehensively analysed and reconstitution of the conceptual fixture structure is realized.And the theory and methodology is lastly exemplified, where a new approach of fixture design automation is explored.