<p>This article focuses on the delamination defect between the metal liner and the wrapping layer of the large-volume cylinder with steel liner and carbon fiber hoop wrapped during the manufacturing process through conducting burst, pressure cycle, and other tests on five newly manufactured and two in-service gas cylinders, and using methods such as visual examination and sound detection and DR test etc. The results show that the performance of seven gas cylinders meets the requirements of the standards, and the DR test method is feasible. The results also show that the metal liner will expand and fit well with the wrapping layer when gas cylinders are filled at the pressure much lower than the nominal working pressure (such as 3MPa). However, with the using of gas cylinder, the fit of gas cylinder under normal pressure will appear random performance, the fit of some gas cylinders can be improved, and others maybe will expand; The delamination between the metal liner and the wrapping layer has little effect on the safety performance of the gas cylinder.</p>