To identify the damage location of the cup-tower with abrupt change in stiffness along height direction, a method based on dual-indicator of modal is proposed. Vibration Mode Difference Index is used to identify the damage in the stiffness changing point of the cup-tower firstly, then the Modal Flexibility Index is used to detect other sections damage, so the false alarm is avoided. The influence of three factors, including environment, modal identification errors and incomplete measurement points, to the dual-indicator method are discussed. The numerical simulation calculations show that the method can identify the damage location effectively, and the three factors have little effect on damage localization.