Abstract: Comparing to common offshore drilling and onshore drilling, deepwater drilling is more dangerous and expensive. It is imperative to develop a better casing design method, which can avoid or reduce down-hole accident caused by improper design. Since the scarce consideration of deepwater drilling features in SY/T 5724—2008 casing string strength design method, it is of great importance to research on a competent casing design methodology for deepwater drilling. In this paper the most dangerous operating conditions in deepwater drilling is considered, and burst, collapse and axial loads are analyzed and calculated. An example is given to show that the primary design method does not meet the need of deepwater casing design, and deepwater drilling conditions have a crucial influence on casing selection. This research achievement has also provided references to the design and application of the onshore and shallow water well casing strength design.