Abstract: Detecting symmetries of B-Rep models can greatly improve the efficiency of CAE analysis.The efficiency of the existing methods is quite low because all the local symmetries of B-Rep models must be detected in advance.A method,based on partial prior recognition,is proposed to detect the global symmetries for B-Rep models.The congruent face set is taken as the unit for symmetry detection.Firstly,the priori knowledge is used to quickly determine the part of the local symmetries.Secondly,the candidate symmetry identification range is shrunk gradually by geometric reasoning.Consequently,the global symmetries of the B-Rep model are determined.Experimental results show that the proposed method is robust and fast.