Bellows technology is mainly used for packer complex wells to deal with lost circulation,kick,water encroachment or collapse and other accidents,to ensure the smooth progress of the complex areas of deep drilling.The article describes the expansion bellows geometry,the finite element method analysis of the different thickness of the mechanical characteristics of the expandable bellows,and the scene example calculation.The results showed that as the bellows wall thickness increased,the desired bulging pressure increased,the bellows also increases the maximum strain;bellows stress increases with the pressure increasing,due to the bellows segment mutual influence,stress fluctuated;bellows strain experienced increasing,stability and continues to increase and the stage of stability;pressure reaches a certain level,the strain of the bellows to stabilize this stage,although the pressure increases in this stage,the deformation is not increased.If the pressure further increases,the bellows may rupture to be failure.