Abstract: Aiming to flexible customer's needs,product variant design method reusing part instance sufficiently was presented.The solutions of dimension constraint conflict transferring and postponing were put forward based on the definitions of dimension modification probability and part variant requirement through the analysis of dimension constraint conflicts resulting from part instance reuse.And the statistical models of dimension modification probability and part variant requirement were established respectively.Then,aiming to the customer preference loss due to part instance reuse,the compensation function of customized characteristic indexes was proposed.A modified customer preference loss model was constructed based on Taguchi's quality loss functions.Finally,an example was given to verify the proposed methods.The results show that selecting the part instances that have minimal affection on customer's requirements during product variant design can meet customer's requirements and decrease the cost of customized product and shorten lead-time effectively.