To support better product variety design oriented to customer, a planning approach for product family based on function-structure (FS) unit was presented. In this approach, for basic function and extending function of product family from the clustering of customer requirements, function and structure were decomposed by iterative mapping of function-behavior-structure (FBS), so as to build multi-level FS units. Afterwards, characteristic parameters and value range of product family and its FS units were resolved by the method of quality function deployment (QFD). And the method which combined function flow with IDEF0 was applied to construct function model of bottom FS units for FBS-based FS decomposition model of product family. In addition, based on this function model, multi-level FS modules of product family were established by pedigree clustering, and basic FS modules and extending FS modules were fixed on. Thus basic module families and extending module families were constructed by integrating structure of FS unit and its characteristic parameters, and eventually product family planning was realized. Finally, this method was applied to product family planning of stacking crane, where FS modules of stacking crane and its BOM model of product family was founded, and the feasibility and validity of the method were proved.
