As the exploration and development of deep carbonate reservoirs, new areas and shale oil and gas is strengthened, the stratigraphic conditions and the medium environments of oil and gas fields become more complex and demanding, and failure accidents happen from time to time, such as tubing/casing string deformation, connection leaking, collapse and fracturing. In addition, wells with special structure and special process and the special stimulation measures ask for new requirements on tubing/casing string. As a result, tubing/casing string is faced with a series of new challenges and difficulties. After over 10 years' research, a series of experimental research progresses and important technological achievements have been obtained to meet the urgent need of reserves and production increase of domestic oil and natural gas industry and solve the technological difficulties of frequent tubing/casing string failure under complicated working conditions, e.g. deep and ultra-deep wells, wells with special structure and special process, and repeated acidizing fracturing of strong acid/high displacement and high-pressure. And these achievements are mainly as follows. First, corrosion material selection and evaluation of tubing/casing pipe, corrosion control and integrity technology of casing/tubing string based on the whole life cycle of a gas well is formed. Second, reliability design & evaluation and supporting technologies for the threaded connection structure and seal of tubing and casing are developed. Third, the casing string technology of "API long round threaded casing + CATTS101 advanced thread compound" suitable for the cost-effective efficient development of low-permeability tight gas wells is researched and developed. Fourth, the test platform and evaluation technology for the structure and seal integrity of casing/tubing string under complicated working conditions (e.g. high temperature and high pressure) are established. Then, based on domestic new needs and new problems in strengthening the exploration and development of oil and gas, some suggestions were proposed on continuing to carry out the research on failure control and integrity of casing/tubing string under complicated working conditions (such as deep layer, acidic environment and shale gas). In conclusion, these technological achievements provide powerful support for the cost-effective development of important oil and gas fields in China.