Abstract: Damage detection indexes have their own characteristic and deficiency. Strain mode is sensitive to structure local characteristic changes and has a great theory foundation. But effect of only using strain mode index is not ideal. As the reaction of structure integral property, structure damage identification index based on frequency can't realize exact locations of damage, though it can be measured conveniently with high precision and widely used in engineering. In order to locate precisely and be applied in engineering, a new practical combination index based strain mode and frequency is presented. Theory analysis and mathematical simulation indicate those combination indexes of low-order and high-order mode can identify damage existence and locate exactly for a single crack and multi-cracks.