Abstract: To probe into the feasibility of optimizing the casing program of deep andultra-deep wells under complicated geological conditions using expandable casing techniques, theoretical analysis and finite element simulation are applied to analyze and demonstrate the new casing program plan of using the ?193 mm and ?139.7 mm expandable casing. What’s more, the finite element simulating calculation of the casing strength after expansion is conducted. Results show that two layers of casing can be added below the ?244.5 mm casing by using the new casing program. The extent of expansion can be selected according to requirements. The strength of the 110ksi and 80ksi steel grade casing after expansion is qualified. It is considered that the expandable casing techniques deserve exploration to solve the problems of deep and ultra-deep wells drilling under complicated geological conditions.