E Every company in petroleum industry aims to recover as much oil and gasas possible at a minimum cost. Therefore, the planning of drilling process have to choose the best method matching with the subsurface condition. One of the most important parts of drilling operation is the casing design. The main function of casing is to maintain hole stability during drilling process. In other that, it connects the surface and the oil – gas reservoir during production process. The first step in the casing design is determine the depth and the position at casing to be set and cemented. After that, we have to calculate all the pressures exerted on the casing string of casing such as burst, collapse, and tension. These pressures will affect the strenght of casing at the time of installation as well as during the production process. The amount of pressure, exerted on the casing, will determine the size, grade, weight, and exerted type of connection casing used. This final project evaluate casing design of exploration well X-9,Prabumulih, South Sumatera. The evaluation focuses on casing setting depthand suitable casing grade selection that well result in optimum casing string interm of safety and economic. This study uses Maximum Load method andsome assumption there is 1/3 bottom hole pressure and lost return with mud. Isincerely hope that this study can be used to evaluate the best casing design and safe.