Puguang Gas Field is the largest high acid marine strata mono-block gas field found in China so far. As the geologic structure is extremely complex, the target stratum is ultra deep, the drilling is rather difficult and high risk, facing so many world-classic engineering problems as high deviation, cavy, blowout, leakage, hard formation, poison, and etc. This paper analyzes the complicated geological characteristics in Puguang gas field, proposes the optimization idea and technique of well structure design and tubing selection, coming up with four casing program optimization schemes according to the knowledge and demand of development, and introduces the application effect and corresponding analysis. The optimization design for well structure achieved to seal off necessary sections of stratum by the simplest casing program, provided the maximum wellbore size,to ensure the cementing quality , meet with the high productivity requirement, and reach the final goal of developing the gas field in a safe and economy manner.