Based on the distributed optical fiber sensing technology, the high density strain information was used to identify the de-bonding defects in the bonded structure, and the research on the identification method of the de-bonding defect was carried out with the insulation foam bonding aluminum alloy structure as the research object. The effect of de-bonding defect detection was studied by using the distributed optical fiber sensor network installed on the metal cantilever beam structure, considering the relative position of fiber and heat-insulating foam, strain level and de-bonding area of heat-insulating foam. The results were verified by bending test of aluminum alloy cantilever plate with heat insulation foam. The results indicated that the distributed optical fiber sensor buried in the adhesive layer was sensitive to the de-bonding defect. The high-density strain information collected before and after de-bonding presented obvious differences, and the strain difference curves in the de-bonding area boundary showed obvious oscillation phenomenon. Therefore, the distributed optical fiber sensor network buried in the bonding layer of the bonding structure can effectively identify the de-bonding defects on the layout path.