Abstract: The author considers that with the commissioning of the West to East Gas Pipeline Project, to insure offering gas to consumers in a continuous and safe way, the gas storage must be constructed, and existing salt-caverns reconstructed into gas storage will speed up the development of underground gas storage and reduce construction investment compared with the construction of new wells and caverns The process during the reconstruction is expounded thoroughly, and several crucial technologies are resolved and applied in practice, such as long casing milling, cavern tightness test, which can be taken as an important solution for other salt-caverns gas storage in construction. The technology provides a technical bank for our future construction of salt-caverns gas storages.