Abstract: By a large number of investigation and failure analysis on fracture failure of high strength casings(yield strength≥140 ksi or 965 MPa), it was considered that the higher strength grade of the casing was, the more toughness required for the casing material was. The high strength casing fracture was mainly related to their low toughness that was not satisfied with its strength. In order to solve radically high strength casing fracture problem, casing fracture failure analysis and research should be done first to find out the fracture causes, and then technical standard should be established in accordance with failure analysis and research results, and some measures should be taken to carry out the technical standard.