History design scheme is helpful in welding fixture design characterized by complexity and individuation.To improve the scheme design efficiency of welding fixture, a multi-layer case reasoning method based on the extension reuse of design knowledge was presented.Welding station information model based on knowledge reuse was introduced by analyzing various fixture design features,and the repository of fixture design based on basic element model was established. Then the extensible model of knowledge reuse was also built.With the use of dopting multi-layer case based reasoning method and calculating the similarity based on basic element feature,the best case was obtained by retrieving the similar welding station composed by shape feature and assembly feature from inside out. Finally, this method was proved to be effective through the verification of the study on an rear floor assembly.
