According to the different applications, the casing diameter of the finished large diameter engineering well is usually 450～1300mm, the large sizes of borehole and casing is one of the marked features of this kind of project. The common methods of casing running and connection as well as the design principles of casing strength for large diameter engineering well were briefly introduced. Combined with the engineering case, the paper clarifies that as long as with the scientific design of casing strength and rational methods of casing running and connection, the casing with weight about 300t also can be safely run by the rig with 100t lifting force.