In order to improve the drilling economic benefits, reduce construction risk and decrease non-production time in Rumaila oilfield of Iraq, the research on casing program optimization has been carried out. Using the design method of inner to outer and bottom to top, according to the formation pressure and combined with the geological characteristics and drilling difficulties, the structure of 3-layers casing program is adopted, the 1st spud is drilled to 6 m above the top of Dammam formation, the 2nd spud is drilled into 8～15 m of Sadi formation and the 3rd spud is completed at the depth of 50 m after drilling through the reservoir. According to the actual needs of the development of Rumaila oilfield and the string size in subsequent operation, and combined with the industry standard, the sizes of drill bits and casings for each spud are determined. Through the safety analysis on the casing string, it is found that L80 casing can not only meet the operation requirements, but also can meet the technical requirements of the safety coefficients of anti-extrusion not less than 1125, anti-internal pressure not less than 110 and tensile resistance not less than 125, and the casing strings can be put down smoothly in each spud. This technology has been successfully applied in 25 wells, the average construction period is shortened by 1533d and the average non-production time is decreased by 86 percentage. The research results show that the optimization technology of the casing program in Rumaila oilfield of Iraq has resolved many complicated problems resulted from multi-zones circulation loss, large shale collapse, sulfur-bearing water invasion, high permeability of reservoir and some othrers, so as to ensure the safe drilling under the complex geological conditions. This technology is helpful to improve the overall drilling level in Rumaila and has a broad market prospect and promotion value.