The damage process of hydroxyl-terminated polybutadiene(HTPB) propellant/liner adhesive interface was observed by scanning electron microscope(SEM)in situ tension system. The real-time SEM images of deformation and failure for interface were collected. The micro mechanism of deformation and failure of adhesive interface was analyzed combining with the macroscopic stress(σ)-strain(ε) curve. Results show that the tensile failure process of adhesive interface can be separated into four stages:l inear interval with larger slope(0 < ε < 5%), linear interval with smaller slope(5% < ε < 25%), nonlinearity interval(25% < ε < 29%) and failure interval(29% < ε < 35%). The two specimens used in verification test reach their ultimate stress when strain arrives at 25% and 30%, respectively. It is also found that dehumidification of internal grain and interfacial debonding have much to do with the change of mechanical property and interface failure. And the interface failure can be reflected by the laws between dehumidification size and strain: when dehumidification size increases linearly with strain, the specimen does not failure. If the increasing rate decreases or the size does not increase, the specimen are damaged.